SOUTHWEST ARIZONA/SOUTHEAST CALIFORNIA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 300 PM MST TUE JAN 21 2003 .SYNOPSIS... A WEAK AREA OF LOW PRESSURE AND SOME HIGH LEVEL CLOUDS WILL DRIFT THROUGH SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA TONIGHT THROUGH THURSDAY. HIGH PRESSURE ALOFT WILL STRENGTHEN BY FRIDAY AND INTO THE WEEKEND...FOR MORE SUNSHINE. WE CAN ALSO EXPECT A WARMING TREND BY THE WEEKEND ALONG WITH MORE DRY WEATHER. .DISCUSSION... 18Z MODEL DATA INDICATED LOW-AMPLITUDE VORT LOBE NEAR BLYTHE AND RACING EAST. STRONGER SYSTEM SEEN NEAR RENO WITH HUGE 500MB RIDGE BUILDING OFFSHORE CALIF...PER LATEST RUC. LOCAL TEMPS SLOWLY WARMING IN RESPONSE TO SUBDUED SUNSHINE AND BOUNDARY LAYER TEMPS WARMING SLOWLY AS WELL. IN FACT SOUTH MTN TEMP VS KPHX INDICATED STRONG INVERSION THAT WILL LIKELY BE AROUND HERE AGAIN TOMORROW MORNING. PROGGED SOUNDINGS SHOW BEST WARMING ALOFT IN THE VERY UPPER LEVELS WHILE 850 TO 700 MB TEMPS LITTLE CHANGED BY WED MORNING. WITH DEW POINTS LTL LOWER...EXPECT LESS OF A CHANCE OF FOG HERE. REPORT FROM ROOSEVELT INDICATED LESS THAN 100 YARDS VSBY THERE EARLY MORNING HOURS. DEW PT SPREADS SHOULD ALSO BE AT OR ABOVE 3 DEG F WED AM. ZONE 24 COULD BE A MARGINAL SITUATION EVEN THOUGH ETA 850 RH VALUE LOWERS SOME 20 PCT FROM 12Z TODAY. WILL NEED TO WATCH TRENDS THIS EVENING. IN THE LONGER RANGE WE WILL SEE FURTHER WARMING ALOFT...ULTIMATELY MIXING DOWN TO LOWER LEVELS AND SFC. WILL FOLLOW MODELS AND CONT. SIMILAR MAX/MINS FROM OLDER PACKAGE. GFS AND UKMET SIMILAR IN THE RISE/FALLING HEIGHTS OVER AZ LATE THIS WEEK. DURING THE WEEKEND HEIGHTS AND THIKNESSES BUILD AGAIN...BUT OVER CALIF LEAVING AZ WITHIN CONTINUED DRY PATTERN. SIPPLE .PSR...NONE. az SOUTHWEST ARIZONA/SOUTHEAST CALIFORNIA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 940 AM MST TUE JAN 21 2003 .SYNOPSIS... A COUPLE OF WEAK PACIFIC LOW PRESSURE SYSTEMS WILL BRING SOME CLOUDINESS ACROSS SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA TODAY AND AGAIN THURSDAY. OTHERWISE...HIGH PRESSURE ALOFT WILL BRING A RETURN TO MOSTLY SUNNY DAYS THROUGH THE WEEKEND. WARMING WILL ALSO BEGIN ON WEDNESDAY WITH TEMPERATURES ABOVE NORMAL FOR LATE JANUARY...ESPECIALLY LATER THIS WEEK AND INTO THE WEEKEND. .DISCUSSION... 12Z UPR AIR DATA SHOWED THE NW FLOW ALOFT AT YUMA/TUS AND FGZ WITH SOMEWHAT HIGHER DEW POINTS IN THE 8K TO 18K FOOT LAYER. THIS MOISTURE IS ABOUT ALL THAT REMAINS AFTER THE CLOSED LOW OPENED UP AND ACCELERATED THRU AZ. PRECIP ENDED ACROSS SRN GILA COUNTY AND BY 15Z THE 700MB TROF EXTENDED FROM NW NM ACROSS GRAHAM COUNTY. SHORT WAVE RIDGE WAS NEAR KINGMAN AND A COUPLE MINOR RIPPLES SEEN OVER OUR WRN ZONES AND RUC/AVN WERE IN GOOD AGREEMENT WITH THESE WEAK FEATURES. ONLY GLITCH IN OUR GOOD WX SEEN AROUND THE FAR EASTERN PORTIONS OF OUR CWA...AND EASTWARD...WHERE PATCHY FOG IS IN THE PROCESS OF DISSIPATING. DO NOT EXPECT ANY UPDATES TO AM PACKAGE. IN THE LONGER TERM...MODELS CONTINUE TO ADVERTISE A FULL-LATITUDE RIDGE FROM OFFSHORE BAJA...NORTHWARD ALL THE WAY TOWARD THE BC COAST BY 00Z. IN FACT 12Z AVN RUN INDICATED SLIGHTLY HIGHER 500MB HEIGHTS COMPARED TO PREVIOUS RUN. DPROG/DT FOR 12Z THURSDAY SHOWS JET CORE WINDS AT 300MB WILL SLIP LTL FARTHER SOUTH THAN EARLIER PROGGED. A STRONG SUBSIDENCE PATTERN IS ALREADY UNFOLDING AND THIS DVV WILL DOMINATE OUR WEATHER THRU 48 HRS. AT THIS TIME...SEE NO REASON TO BEEF UP OR TRIM BACK ON CLOUD COVER FORECASTS FOR OUR CWA LATER THIS WEEK. NO UPDATES PLANNED. SIPPLE .PSR...NONE. az SOUTH CENTRAL AND SOUTHEAST COLORADO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PUEBLO 400 AM MST TUE JAN 21 2003 SHORT TERM DISCUSSION...(TODAY AND TONIGHT). ...BIG CHALLENGE TODAY IS TEMPERATURE FORECAST ON THE PLAINS... WELL...BASED ON RUC/MESO-ETA PROGNOSTICATIONS FOR TODAY...THE SHALLOW ARCTIC AIRMASS WILL OVERSPREAD MOST OF THE PLAINS TODAY... PLAYING HAVOC WITH TEMP FORECASTS. BOTH THE RUC AND MESO-ETA SHOW LIGHT EAST TO SOUTHEAST WINDS AT KPUB THROUGH THE DAY TODAY. LOW LEVEL RH PROGS FROM THESE MODELS ALSO SHOW A TONGUE OF MOISTURE MAKING IT UP THROUGH THE LOWER ARKANSAS RIVER VALLEY THIS MORNING... BEFORE RETREATING THIS AFTERNOON. SO FAR...THIS ALL LOOKS GOOD AS PER RUC/MESO-ETA FORECASTS...WE NOW HAVE A WIND 060/07 KTS AT KPUB AND LOW CLOUDS AS FAR WEST AS KLHX. OVER THE PLAINS ADJACENT TO THE MOUNTAINS...WON'T EXPECT MUCH IN THE WAY OF LOW CLOUDINESS TO MAKE IT IN...BUT WOULD EXPECT MUCH COOLER AIRMASS TO TAKE OVER...AS LIGHT EAST WINDS KEEP IT PACKED IN FOR MUCH OF THE DAY. SO...HAVE SIGNIFICANTLY LOWERED TEMPERATURE FORECASTS OVER THE EAST FOR TODAY...ON THE ORDER OF 10 DEGREES. HAVE ALSO KEPT FOG AND CLOUDS IN THE GRIDS...MAINLY FROM ABOUT KLHX EASTWARD (ALTHOUGH COULD BE A BRIEF BOUT OF LOW CLOUDS KPUB VCNTY EARLY THIS MORNING). FROM THE SOUTHEAST RANGES WESTWARD...REALLY NOT MUCH CHANGE IN TEMPS TODAY VS YESTERDAY AS ARCTIC AIRMASS AS LITTLE OR NO EFFECT. HOWEVER...MAYBE A FEW DEGREES COOLER DUE TO COOLING ALOFT ASSOCIATED WITH PASSING DISTURBANCE TO OUR SOUTH. TONIGHT...GRIDS HAVE SNOW SHOWERS RETURNING TO THE CENTRAL/SOUTHWEST MOUNTAIN AREAS. THIS STILL LOOKS GOOD AS ETA MODEL STILL FORECASTS CLOUDS/PRECIP THESE AREAS...MAINLY AFTER MIDNIGHT...AS ENERGY COMING ONSHORE OVER THE WEST COAST THIS MORNING MAKES ITS WAY THROUGH COLORADO. MAY NEED TO INCREASE POPS AND ADD SNOW AMOUNTS FOR THE CENTRAL MOUNTAINS TONIGHT...IF SYSTEM HOLDS TOGETHER ON ITS TREK ACROSS THE GREAT BASIN TODAY. SYSTEM TO HAVE LITTLE AFFECT ON REMAINDER OF SOUTHERN COLORADO...SAVE FOR A LITTLE INCREASE IN MID/HIGH LEVEL CLOUD COVER. /LW LONG TERM DISCUSSION...(WEDNESDAY-MONDAY). WEDNESDAY/THURSDAY...PASSAGE OF UPPER JET ALLOWS LEE TROF TO HANG ON...EXPECT WARM TEMPS I25 CORRIDOR AND COOLER TEMPS FAR E TO REMAIN. THURSDAY...AVN BRINGS IN MORE MOISTURE THROUGHOUT THE ATMOSPHERE WITH PASSAGE OF S/W TO OUR NORTH...WHICH AS A RESULT MAKES UPPER FLOW MORE WEST OVER OUR AREA. INCREASED MOUNTAIN WINDS (AOA 10KFT) AND ADDED MOUNTAIN POPS TO LA GARITA/SAN JUANS FOR THIS FLOW PATTERN. INCREASED WINDS FAR EAST PLAINS AS GRADIENT INCREASES THURSDAY BETWEEN HIGH PRESSURE AND LEE TROF. WITH WINDS...LEFT CURRENT FAR EAST PLAINS TEMP GRIDS IN THE LOWER 40S...NOTING HOWEVER THAT GUIDANCE IS STILL RUNNING IN THE LOWER 30S FOR LAA AND KSPD. FRIDAY/SATURDAY...NORTHWEST FLOW RETURNS AS S/W SWINGS SOUTHEAST INTO THE NORTHERN PLAINS...AND USHERS THE ARCTIC HIGH OUT OF THE FAR SOUTHEAST PLAINS. SIGNIFICANT DRYING ALL LEVELS LEAVES NO POPS WITH ABUNDANT SUNSHINE. NW FLOW AT SURFACE WILL BE COOLER...HOWEVER COMBINED WITH SLIGHT DOWNSLOPE COMPONENT AND SUNSHINE...TEMPS DON'T CHANGE MUCH FROM THURS. SATURDAY...LEE TROF REMAINS FOR MORNING HOURS...THEN NEXT SYSTEM BEGINS TO MOVE INTO THE AREA SATURDAY MIDDAY. ADDED POPS SOUTHWEST MOUNTAINS THIS DAY. FROPA ON PLAINS LEAVES 700MB TEMPS -2/-4...VERY SIMILAR TO WHAT THEY HAVE BEEN MOST OF THE WEEK. DEGREE OF CLOUDINESS WILL AFFECT TEMPS. SUNDAY/MONDAY...RIDGE MOVES OVERHEAD SUNDAY...WARMS 700 TEMPS TO NEAR 0C. LEE TROF EXTENDS SOUTHWARD FROM LEE LOW IN MONTANA...WHICH PROGRESSES EASTWARD WITH S/W INTO THE OHIO VALLEY ON SUNDAY. S/W RIDGING RETURNS BEHIND...AND TEMPS WARM SLIGHTLY AS A RESULT. NO CHANGES HERE. -KC .PUB...NONE. co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 1030 PM EST TUE JAN 21 2003 MAIN FCST CONCERNS OVERNIGHT ARE LES TRENDS/AMOUNTS. WV IMAGERY AND RUC ANALYSIS INDICATED CONTINUED FAST WNW MID/UPR LVL FLOW THROUGH THE WRN LAKES BENEATH TROF FROM NRN MANITOBA AND NRN ONTARIO INTO NRN QUEBEC. AT THE SFC...LK INDUCED TROFFING AGAIN WAS EVIDENT FROM SE LK SUPERIOR THROUGH NORTH CNTRL UPR MI TOWARD ONTONAGON SEPARATING WRLY LAND BREEZE FROM NNW (330) FLOW ACRS LK SUPERIOR. KMQT 88D INDICATED VEERING TREND WITH LIGHT TO MODERATE SNOW BANDS AS MAX RETURNS ONLY TO 20 DBZ WITH RELATIVELY ORGANIZED APPEARANCE. LAND BREEZE WAS ALSO KEEPING LES MAINLY OFFSHORE FROM MARQUETTE WITH SOME -SHSN JUST BRUSHING THE SHORELINE AND FLURRIES FARTHER INLAND. EXTREMELY COLD/DRY AIR (H8 TEMPS TO -25C, INVERSION HGTS NEAR 850 MB, SFC DEWPOINTS UPSTREAM FROM -20 TO -35 F) WAS ALSO INHIBITING SNOWFLAKE GROWTH AND WILL LIMIT ACCUMULATIONS DESPITE AMPLE INSTABILITY. 00Z ETA CONTINUES TREND FROM EARLIER RUNS WITH BEST LOW LVL CONVERGENCE IN THE WEST INTO ONTONAGON COUNTY. OVER THE EAST...LK TROF INFLUENCE KEEPS MOST FAVORABLE CONVERGENCE NEAR THE SE END OF THE LAKE. SO...MODEST ADDITIONAL ACCUMULATIONS FOR ADVY AREAS LOOK ON TRACK WITH TOTAL AMOUNTS OF 4-5 INCHES POSSIBLE AS HAS BEEN THE CASE OVER RECENT NIGHTS. OTHERWISE...LIGHTER 1-2 INCH AMOUNTS EXPECTED. BEST CHANCE FOR AN INCH OR TWO IN MARQUETTE COUNTY WILL BE EAST OF HARVEY GIVEN INFLUENCE OF LAND BREEZE AND PERSISTENT 330 FLOW. FARTHER INLAND...MAINLY JUST A DUSTING EXPECTED. FCST TEMPS ARE ON TRACK WITH READINGS INLAND ALREADY WELL BELOW ZERO. DECOUPLED WINDS AND CLEARING AWAY FROM THE LAKE SHOULD ALLOW SOME READINGS TO DROP INTO THE -10 TO -15 F RANGE. .MQT...LAKE EFFECT SNOW ADVISORY TONIGHT/EARLY WED MIZ002-006-007-009-085. WINTER STORM WATCH WED NIGHT INTO THU MIZ002-006-007-009-085. HEAVY FREEZING SPRAY WARNING LAKE SUPERIOR. KC mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 940 PM EST TUE JAN 21 2003 EASTERN UPPER MICHIGAN IS AGAIN POISED FOR A VERY COLD NIGHT...WITH EVEN COLDER AIR JUST UPSTREAM ACROSS SW ONTARIO (AROUND -25F) THAN WAS THE CASE LAST NIGHT. THIS FRIGID AIRMASS WILL PRESS S/SW...AGAIN SPREADING ACROSS THE EASTERN UP AND INTO AT LEAST FAR NORTHERN LOWER MICHIGAN. RECORD LOW FOR WEDNESDAY AT SSM (-22F) MAY BE IN JEOPARDY...AND ADDED MENTION OF NEAR RECORD LOWS TO CHIPPEWA COUNTY FORECAST OVERNIGHT. OTHERWISE...LAND BREEZE WILL EVENTUALLY PUSH SNOW SHOWERS INTO WESTERN SECTIONS OF CHIPPEWA AND MACKINAC COUNTIES (PERHAPS EVEN WEST OF THESE COUNTIES). SOUTH OF THE STRAITS...IR IMAGERY DEPICTING DECREASING COVERAGE OF CLOUD TOP TEMPS -30C TO -35C SUGGESTS THAT WEAK 700-500 MB QG FORCING...COVERAGE OF MID CLOUDS AND ASSOCIATED ENHANCEMENT OF LAKE EFFECT SNOW BANDS ARE DIMINISHING...IN LINE WITH 0Z RUC40 FORECAST PARAMETERS. HOWEVER...OVER LAKE INSTABILITY AND INVERSION HEIGHTS 5-6 KFT WILL CONTINUE TO SUPPORT LAKE EFFECT SNOW SHOWERS...MOST WIDESPREAD IN NW FLOW COUNTIES OF NW LOWER MICHIGAN (ALSO RAISED POPS TO LIKELY PER RADAR TRENDS ACROSS SW COUNTIES) AND ALONG THE LAKE HURON SHORELINE FROM E CHEBOYGAN THROUGH PRESQUE ISLE TO N ALPENA COUNTY. 850 MB TEMPS -22C TO -26C WILL CONTINUE TO LIMIT SNOWFLAKE GROWTH...WITH SMALL FLAKE SIZE HOLDING HIGHEST NIGHTTIME ACCUMULATIONS TO THE 1-3" RANGE PER PREVIOUS FORECAST. OTHERWISE...MADE OTHER MINOR ADJUSTMENTS...MAINLY TO WIND FORECASTS...OVERNIGHT. .APX...NONE. ROWLEY mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 335 PM EST TUE JAN 21 2003 12Z RAOBS/LATEST WV LOOP AND RUC ANAL SHOW ARCTIC VORTEX OVR ONTARIO WITH WNWLY FLOW FM SW CAN INTO THE MID ATLANTIC STATES. VERY COLD AIR IN PLACE OVR THE NW GRT LKS...WITH H85 TEMPS IN THE -20C TO -25C RANGE OVR LK SUP/CWA. SHRTWV EMBEDDED WITHIN THE WNW FLOW ACCOMPANIED BY 140KT H3 JET MAX OVR SD HAS CAUSED LO PRES TROF OVR THE WRN CWA WITH ENHANCED CNVGC ACRS THE KEWEENAW. VIS SAT PIX SHOW A DOMINANT LES BAND STREAMING ON LAND NR CMX...WHERE VSBY HAS BEEN AOB 1/2SM FOR THE LAST FEW HRS. CONSIDERING BLSN/WND CHILLS ARND -20F...ISSUED WINTER WX ADVY FOR NRN CMX COUNTY FOR THE AFTN. SN ACCUMS DO NOT APPEAR TO BE EXCESSIVE...AS 12Z INL SDNG SHOWS INVRN HGT ARND H9 WITH VERY DRY AIR ABV INVRN...LO H85 TEMPS NEGATIVELY IMPACTING SN GROWTH...AS WELL AS SFC DWPTS -15 TO -25F OVR MN ARROWHEAD/NW ONTARIO. OTRW...MQT 88D SHOWS NMRS WND PARALLEL LES BANDS STREAMING INTO THE ERN ZNS...WHERE LES ADVY CONTINUES IN CNVGC ENHANCED BY ELY LAND BREEZE OFF ONTARIO. ANOTHER SHRTWV NOTED MOVG SE THRU ALBERTA. MAIN FCST CONCERNS IN SHORT TERM INCLUDE GOING HEADLINES/LES TRENDS ASSOCIATED WITH SHRTWVS MOVG ESE IN WNWLY FLOW ALF. 12Z ETA/RUC APPEAR TO HAVE BEST HANDLE ON PRESENCE OF SHRTWV NOW APRCHG FM THE WNW. ALL MODELS APPEAR TO HAVE GOOD HANDLE ON LOCATION OF NXT SHRTWV NOW OVR ALBERTA. ETA INDICATES ENHANCED H85-5 QVECTOR CNVGC ASSOCIATED WITH FIRST SHRTWV DPVA MOVES SE OF CWA AFTR 00Z. IMPACT OF THIS SHRTWV IS TO SHIFT THE LLVL WNDS TO MORE NNW BTWN 00Z AND 06Z BEFORE APRCH OF ALBERTA SHRTWV AND MORE H85-5 QVECTOR CNVGC CAUSE FLOW TO BACK A BIT MORE NW LATER. AS A RESULT OF SHIFTING WNDS...ETA SHOWS ENHANCED H95 CNVGC SHIFTING AS WELL. OVR THE W... CNVGC MAX OVR NRN CMX COUNTY DRIFTS INTO ONTONAGON/GOGEBIC COUNTIES BY 06Z WITH VEERING FLOW OVR LK SUP AND INTENSIFIES AS IT ENCOUNTERS MORE WLY FLOW IN NW WI/IWD THEN SLOWLY BACK N INTO MORE ONTONAGON COUNTY TOWARD DAWN AS FLOW BACKS LATE. WITH DIMINISHING WNDS AND VEERING FLOW TO MORE UNFVRBL NNW...XPCT CONDITIONS TO IMPROVE OVR NRN CMX COUNTY. BUT XPCT DETERIORATING CONDITIONS OVR GOGEBIC/ONT ZNS AS CNVGC MAX SHIFTS INTO THESE AREAS. LES CHART WOULD SUG 4"/6 HRS OF SN WITH INVRN HGT XPCTD NR 5K FT...BUT SHIFTING WNDS/CNVGC/ DRY AIR UPSTREAM SUG MORE MODEST AMTS...PERHAPS 2-3"/6 HRS. BEST SHOT FOR MINIMAL ADVY SN WL BE WAKEFIELD TO ROCKLAND...SO WL POST MINIMAL LES ADVY EVEN THOUGH LLVL WND SPEEDS (AND BLSN/WND CHILLS) FCST TO DIMINISH AS SERIES OF SHRTWVS PASSING TO S MAY RESULT IN SOME ENHANCEMENT AND FOCUS CNVGC. OVR THE E...ETA SHOWS H95 CNVGC ENHANCED OVR LUCE COUNTY WITH LAND BREEZE OFF VERY COLD AIRMASS IN ONTARIO CONTG. WL CONT GOING ADVY THESE ZNS DESPITE SHIFTING WNDS. LONGER FETCH ACRS LK SUP/HIER INVRN HGT WL SUPPORT SOMEWHAT HIER ACCUMS THAN FCST OVR THE W. NCNTRL SN BELTS WL REMAIN SOMEWHAT SHELTERED...BUT MORE NLY FLOW FOR A FEW HRS WL LIKELY SHIFT LES BANDS INTO AT LEAST ERN MQT COUNTY FOR A TIME. MIN TEMPS WL BE LOWEST ALG THE WI BORDER...WHERE LLVL FLOW HAS BEST CHC TO BE UNAFFECTED BY LK SUP MODERATION AND WHERE NOTHING MORE THAN FLURRIES WL FALL. SHRTWV FM ALBERTA FCST TO MOVE TO WI LATE TNGT PROGGED TO CONT QUICKLY SE INTO THE SCNTRL LKS ON WED. BUT ANOTHER MORE SHEARED LOOKING SHRTWV FCST TO DROP INTO NW MN BY 00Z THU. ETA SHOWS CONSIDERABLE WEAKENING OF H95 CNVCG MAXIMA DURG DAY AS WEAK SHRTWV RDGING/H85-5 QVECTOR DVGC BTWN THE DEPARTING AND APRCHG SHRTWVS DOMINATE. AVN AND ESPECIALLY ETA SHOW LLVL FLOW BACKING A BIT DURG DAY IN ADVANCE OF NXT SHRTWV. DESPITE LACK OF FOCUSING CNVGC... XPCT LES TO CONT WITH H85 THERMAL TROF -25/-26C LINGERING OVR LK SUP/CWA. LACK OF FOCUS AS WELL AS VERY COLD...DRY AIR WL SUPPORT NO MORE THAN 4" OF SN DURG DAY...ABOUT HALF FCST FM LES CHART GUIDANCE. BUT WL NOT EXTEND ADVYS BEYOND MID MRNG WHEN BEST LLVL CNVGC PROGGED TO DIMINISH. BUT DAY PROMISES TO BE QUITE CHILLY WITH COMBINATION OF STEADY 10 TO 20 MPH WND AND MAX TEMPS SIMILAR TO TDAY (PERSISTENCE OF H85 TEMPS) RESULTING IN WND CHILLS -10F TO -25F. SHRTWV THAT MOVES INTO MN LATE WED FCST TO DIVE SE INTO OH VALLEY THU MRNG. AVN/NGM AND ESPECIALLY ETA HINT ENHANCED DPVA/H85-5 QVECTOR CNVGC MAX WL CROSS OVR CWA DURG WED NGT AS FLOW VEERS FM NW TO NNW. HAVE OPTED TO ISSUE WINTER STORM WATCH FOR GOGEBIC/ONT AS WELL AS ALGER/LUCE/NRN SCHOOLCRAFT WED NGT AS DYNAMICS/DEEPER MSTR/HIER OR WEAKER INVRN IN PLACE WHEN LLVL WND IN FVRBL 320-330 FLOW AND WND SPEEDS FCST WITHIN MIXED LYR UP TO 35KT TO CAUSE BLSN/LWR WIND CHILLS. ALTHOUGH SN AMTS MAY NOT BE EXCESSIVE AND SATISFY ONLY ADVY CRITERIA...FEEL COMBINATION OF FALLING SN...BLSN AND LO WND CHILLS MAY BE ENUF TO JUSTIFY HEIGHTENED AWARENESS. WND CHILL ADVY MAY BE NECESSARY OVR INTERIOR SCNTRL WITH MINS -5 TO -10F AND WND SPEEDS ARND 15 MPH. ETA QUITE AGGRESSIVE AT CRASHING INVRN HGTS/INCRSG H85 TEMPS IN WAKE OF THIS SHRTWV LATE WED NGT AND THU...BUT AVN FCST H85 TEMPS QUITE A BIT LWR (BY ABOUT 5C) INDICATE THAT MODEL WOULD PERPETUATE MORE SGNFT LES LONGER...SO HAVE OPTED TO XTND WATCH INTO THU. KEWEENAW/NCNTRL ZNS WL REMAIN PRETTY MUCH SHIELDED FM SGNFT LES. NOTHING MORE THAN FLURRIES ACRS THE SCNTRL AGAIN. AS UPR HGTS BUILD OVR CWA THU-FRI AND SFC RDGING APRCHS... XPCT LES TO DIMINISH. POTENTIALLY VERY COLD THU NGT OVR INTERIOR WCNTRL CWA AS RDG AXIS MOVES OVHD. ONLY FLY IN THE OINTMENT COULD BE HI CLOUDS ASSOCIATED WITH SHRTWVS DIGGING IN NWLY FLOW ALF. AFTR QUIETER WX BY LATE FRI...00Z/06Z EXTENDED MODELS POINT TOWARD A REINFORCING SHOT OF COLD AIR FOLLOWING COLD FROPA ON SAT. HOWEVER... ALL MODELS INDICATE THE BRUNT OF THIS ARCTIC SURGE TO REMAIN IN CAN...WITH H85 TEMPS FALLING TO -20C OVR LK SUP (VS -25C WITH THIS CURRENT OUTBRK). GOING FCST FOR CHC -SN ON SAT IN ADVANCE OF COLD FNT AND THEN LES ON SUN IN WAKE OF FROPA APPEARS ON TARGET. HOWEVER WL BACK AWAY FM BLUSTERY WORDING ON SUN GIVEN TREND FOR SHRTWV/CORE OR ARCTIC AIR/SHARPEST PRES GRADIENT TO REMAIN N OF CWA. THEN SIGNS OF A SGNFT WARM UP EARLY NXT WEEK AS ALL MODELS SHOW UPR FLOW TENDING TO BCM MORE ZONAL WITH LO PRES DVLPG OVR SW CAN BEFORE TRACKING ESE EARLY NXT WEEK. OPERATIONAL GFS/GFS ENSEMBLE MEAN INDICATE SFC LO WL TRACK OVR SRN CWA/NRN WI TUE...SO WL FCST CHC -SN BOTH MON/TUE. NOT YET READY TO BUY INTO VERY WARM AIR ADVERTISED BY 00Z OPERATIONAL GFS...WHICH SHOWS H85 TEMPS RISING ABV 0C AND PCPN IN THE FORM OF RA...AS ENSEMBLE MEAN FCST H100-5 THKNS QUITE A BIT LWR THAN INDICATED BY OPERATIONAL MODEL. BUT FCST TEMPS EARLY NXT WEEK GO ABV NORMAL WITH NO INDICATION REAL ARCTIC AIR WL RETURN LATER NXT WEEK. COORDINATED WITH APX/DLH. .MQT...LAKE EFFECT SNOW ADVISORY TONIGHT/EARLY WED MIZ002-006-007-009-085. WINTER STORM WATCH WED NIGHT INTO THU MIZ002-006-007-009-085. HEAVY FREEZING SPRAY WARNING LAKE SUPERIOR. KC mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 1040 AM EST TUE JAN 21 2003 THE MAIN CONCERN WITH THIS FORECAST PACKAGE IS THE PERSISTENT LAKE EFFECT SNOWS AND COLD TEMPERATURES FOR TODAY. WV IMAGERY AND RUC SHOWING CLOSED LOW OVER NORTHERN ONTARIO IS EMBEDDED IN A LONGWAVE TROUGH WHICH COVERS MUCH OF EASTERN CANADA. A RIDGE OFF THE COAST OF BRITISH COLUMBIA SEPARATES THIS LONGWAVE FROM ONE OVER THE GULF OF ALASKA. A 125+ KNOT JET RACES DOWN THE LEE OF THE WEST COAST RIDGE AND RUNS THROUGH THE NORTHERN PLAINS...ACROSS THE UPPER MISSISSIPPI VALLEY INTO THE LOWER GREAT LAKES. ONE RATHER SHEARED SHORTWAVE IS OVER NORTHERN LOWER MICHIGAN...FOLLOWED BY ANOTHER OVER THE INTERNATIONAL PEACE GARDENS. YET ANOTHER IS CHASING THE FIRST TWO AND IS OVER NORTHERN ALBERTA. ANOTHER RATHER STRONG SHORTWAVE IS OVER CENTRAL ONTARIO. SURFACE ANALYSIS INDICATE A WEAK TROUGH STRETCHING FROM EASTERN U.P. INTO SOUTHEAST ONTARIO. A BROAD RIDGE IS SPREADING ACROSS THE NORTHERN PLAINS INTO THE UPPER GREAT LAKES. THE SHORTWAVE OVER THE PEACE GARDENS WILL RACE SOUTHEAST AND REACH THE FORECAST AREA THIS AFTERNOON. THE SHORTWAVE OVER THE EASTERN U.P. WILL REMAIN IN PLACE THROUGH THIS AFTERNOON. WATER-850MB DELTA-T'S WILL BE AROUND 26C THIS AFTERNOON. FORECAST WIND CONVERGENCE FIELD SHOWING FAIRLY STRONG LOW LEVEL CONVERGENCE ACROSS THE LAKE SUPERIOR TODAY. THE AIR MASS IS QUITE DRY. PRECIPITABLE WATER AROUND .06 INCH ACROSS THE AREA. ANY LAKE EFFECT SNOWS WILL HAVE TO DERIVE ITS MOISTURE FROM THE LAKE SUPERIOR. LOWEST INVERSION OVER THE WESTERN LAKE SUPERIOR IS AROUND 3K FEET...WHILE OVER THE EASTERN LAKE SUPERIOR IT IS AROUND 4.5K FEET. THE WINDS WILL BE MAINLY OUT OF THE NORTHWEST THIS AFTERNOON. THUS WITH THE LOW INVERSION...SHORT FETCH...AND DRY CONDITIONS OVER WESTERN LAKE SUPERIOR...THUS EXPECT ONLY MINOR ACCUMULATION OF 1 TO 2 INCHES OF SNOW OVER THE WEST TODAY. OVER THE EASTERN COUNTIES...WITH THE HIGHER LOW LEVEL INVERSION...LONGER FETCH...AND GREATER DEGREE OF CONVERGENCE...SNOW ACCUMULATION WILL BE GREATER...ON THE ORDER OF 1 TO 3 INCHES...MAINLY EAST OF MUNISING. WINDS WILL BECOME MORE NORTHWEST THIS AFTERNOON AS THE SURFACE RIDGE PUSHES IN THE UPPER MISSISSIPPI VALLEY. TEMPERATURES SHOULD REBOUND INTO THE SINGLE DIGITS ABOVE ZERO ACROSS THE U.P...EXCEPT FOR AROUND 12 ABOVE FOR ALONG THE LAKE MICHIGAN SHORE. DLG MODELS HAVE COME AROUND TO A SOMEWHAT INTERESTING SOLN FOR TONIGHT. AS THE SHEARED OUT S/WV MOVES OVER THE AREA BETTER MID LVL MOISTURE RETURNS TO THE AREA. THIS SEEMS REASONABLE GIVEN HIGH CLDS OVER MANITOBA/ALBERTA ATTM. AS THIS S/WV PASSES THRU...IT HELPS TO SHARPEN THE LAKE INDUCED TROUGH AND SUPPRESS IT TO THE SOUTH SLIGHTLY. THIS LEADS TO A 350 DEG WIND OVER THE LAKE AS THE ARCTIC BOUNDARY MOVES THRU...WITH THE ETA SHOWING A STRONG LOW LVL CVRG AREA OVER ONTONAGON COUNTY...AS WELL AS CONTINUED CVRG OVER THE EAST (ALTHOUGH MORE FOCUSED INTO AREAS OF WESTERN ALGER COUNTY). WITH THE WEAK PRES GRADIENT OVER THE INLAND AREAS...THERE WILL PROBABLY BE SOME TYPE OF A LAND BRZ SO CVRG COULD BE STRONGER. WOULD NOT BE SURPRISED THAT ONTONAGON/SRN HOUGHTON COUNTIES SEE ADVY TYPE SNOWS (3-6 INCHES) TONIGHT...BUT SINCE THIS IS REALLY THE FIRST RUN OF THE MODELS THAT HAVE SUGGESTED THIS SCENERIO...WILL HOLD OFF ON ISSUING ANY ADVY. HOWEVER...DAY SHIFT MAY NEED TO CONSIDER ONE IF 12Z RUNS ARE SIMILAR. OTHERWISE...WITH 350DEG WIND TONIGHT...MQT COUNTY WILL SEE A LITTLE MORE LES ACTIVITY. BEST ACCUMULATIONS WILL PROBABLY BE NEAR THE SHORELINE (WHERE LAND BRZ WILL ENHANCE LOW LVL CVRG) AND EAST OF MARQUETTE. WILL GO WITH 1 TO 4 INCHES FOR MQT COUNTY. FOR THE KEWEENAW...ONLY 1 TO 3 INCHES WITH 350 DEG WIND DIR UNFAVORABLE. TOUGH CALL FOR GOGEBIC COUNTY...BUT THINK THAT BEST CVRG WILL STAY TO N OF THAT AREA AND LAND BRZ WILL DOMINATE...SO ONLY AN INCH OR 2 THERE. AS FOR WED...LOOKS LIKE WINDS WILL BACK TO THE NW DURING THE MORNING AS THE ARCTIC FRONT MOVES S AND THE LAKE INDUCED TROUGH WEAKENS (ALTHOUGH THE TROUGH MAY NOT WEAKEN AS MUCH AS MODELS SUGGEST WITH SUCH COLD AIR ALOFT). CONDITIONS WILL BE SIMILAR TO TODAY...ALTHOUGH INVERSION WILL BE A LITTLE LOWER DUE TO A LITTLE BIT MORE ARCTIC AIR AS THE AREA GETS BRUSHED BY THE ARCTIC VORTEX. THEREFORE...WILL GENERALLY GO WITH 1 TO 4 INCH FAVORED NW FLOW LES REGIONS. LIMITATIONS FOR BIG SNOW AMTS CONTINUE TO BE POOR SNOW GROWTH POTENTIAL. WITH 850MB TEMPS AROUND -25C...THIS WILL PROBABLY ALSO BE THE COLDEST DAY OF THE WEEK...AND WOULD NOT BE SURPRISED IF THERE ARE A FEW ZERO OR SUB-ZERO MAX TEMP READINGS...ESPECIALLY OVER THE WEST. WILL THEREFORE LOWER TEMPS ON WED SLIGHTLY TO REFLECT THIS THINKING. OTHERWISE...NO CHANGES TO REMAINDER OF FCST. THU COULD BE INTERESTING AS SOME WARMER AIR WRAPS INTO THE REGION FROM THE N ENABLING BETTER SNOW GROWTH. HOWEVER...AT THE SAME TIME DOWNWARD MOTION INCREASES AS THE RIDGE AXIS BUILDS OVERHEAD SO IT WILL BE INTERESTING TO SEE WHAT HAPPENS TO THE LES. SFC WINDS REMAIN NWLY PER ETA...BUT THE GFS IS A LITTLE MORE GENEROUS WITH THE NLY WINDS. THIS WOULD SEEM TO MAKE SENSE GIVEN COLD DOME THAT WILL BE IN PLACE OVER CANADA. WILL KEEP LIKELY POPS NEAR LAKE SUPERIOR. THU WILL BE A LITTLE WARMER...BUT STILL COLD DESPITE THE ETA SHOWING 850MB TEMPS RISING TO -14C AS THERE WILL BE ALOT OF COLD AIR TRAPPED NEAR THE SFC. 00Z GFS STILL SHOWS A DECENT WARMUP...POSSIBLY ABV NORMAL...FOR THE BEGINNING OF NEXT WEEK. .MQT...LAKE EFFECT SNOW ADVISORY TODAY AND TONIGHT MIZ006-007-085. HEAVY FREEZING SPRAY WARNING LAKE SUPERIOR. MRD mi AREA FORECAST DISCUSSION-UPDATED NATIONAL WEATHER SERVICE NORTH PLATTE NE 1210 PM CST TUE JAN 21 2003 WILL UPDATE ZONES SHORTLY FOR INCLUSION OF WINTER WX ADVISORY FOR FREEZING DRIZZLE IN THE FAR SW. PATCHY FREEZING DRIZZLE CONTINUES ACROSS CHASE...HAYES...AND PERKINS COUNTIES THIS MORNING. FCST SOUNDINGS IN THESE AREAS CONTINUE TO INDICATE SOME WEAK LL WAA AND DRY AIR IN THE MID LEVELS. WILL ISSUE THE PRODUCT FOR THESE COUNTIES THIS AFTERNOON...AND IN ALL LIKELIHOOD RE-ISSUE FOR MOST OF THE SW FOR TONIGHT AND TOMORROW WITH AFTN PACKAGE. .LBF...WINTER WX ADVISORY CHASE...HAYES AND PERKINS COUNTIES THIS AFTN CLB AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTH PLATTE NE 930 AM CST TUE JAN 21 2003 WILL UPDATE ZONES SHORTLY FOR COSMETIC CHANGES AND TO EXTEND MENTION OF PATCHY LIGHT FREEZING ACROSS THE WEST AND SWRN ZONES INTO THE AFTERNOON HOURS. RAOB SOUNDINGS AT H5...AS WELL AS ETA MODEL SOUNDINGS INDICATING SOME DRYING IN THE MID LEVELS THIS AFTERNOON BEFORE COMPLETELY SATURATING OVERNIGHT. WITH MOIST LL PROFILES WARMING TO ABOVE -10C TODAY...LIGHT FREEZING DRIZZLE SHOULD CONTINUE. DRIZZLE REMAINS VERY LIGHT PER CALLS TO SHERIFFS DEPTS ACROSS THE SRN AND SWRN TIER OF COUNTIES...SO WILL FORGO ADVZY AT THIS JUNCTURE AND RE-EVAL NEAR NOONTIME. FARTHER NORTH...LIGHT SNOW CONTINUES. COOP ACCUMULATIONS THIS AM ARE INDICATING 1-2 INCHES ACROSS THE SANDHILLS...MAINLY FROM SHERIDAN SEWD INTO LOGAN COUNTY. ETA MODEL INDICATING WEAK MID LVL FRONTOGENESIS FIELD SHIFTING EWD AFTER NOON TIME...SO SNOW TAPERING OFF TO FLURRIES LOOKS REASONABLE. NOTE...DUE TO IFPS UPGRADE...GRIDS WILL NOT BE UPDATED TILL NEAR NOONTIME. CLB FREEZING DRIZZLE/SNOW EVENT MAIN CHALLENGE. SURFACE ANALYSIS FROM THIS EARLY MORNING SHOWS ARCTIC FRONT BACKING TO THE SOUTHWEST WITH COLD AIR DAMMING UP AGAINST CENTRAL ROCKIES. QUICK SCAN OF RADAR MOSAIC SHOWS A WEAK BUT PERSISTENT SNOW BAND ALONG A KCDR TO KBBW LINE. FURTHER SOUTH WHERE FOG AND STRATUS IS ALREADY PRESENT... A LACK OF SEEDER FEEDER FROM DENDRITIC LAYER HAS RESULTED IN AREAS OF FREEZING DRIZZLE. LATEST MODEL RUNS HAVE INITIALIZED MID AND UPPER LEVEL FEATURES DECENT... BUT BOUNDARY LAYER FEATURES ARE ANOTHER QUESTION. GFS FALSELY INITIALIZED A 1006 MB LOW ACROSS EASTERN COLORADO WITH ETA DOING A TAD BETTER. DESPITE THESE DIFFERENCES MODELS EVOLVE PATTERN SIMILARLY THROUGH 48-60 HOURS. WILL LEAN TOWARDS ETA FOR THIS FORECAST BASED ON SLIGHTLY BETTER INITIALIZATION. BIGGEST PROBLEM FOR TODAY IS FIGURING OUT WHERE LIGHT SNOW/FLURRIES VERSUS FREEZING DRIZZLE EXIST ACROSS FA. 06Z RUC APPEARS TO BE BACKING OFF ON ANY SEEDING FROM DENDRITIC LAYER ACROSS SOUTHWEST ZONES THAT 00Z ETA AND GFS INDICATED WOULD OCCUR. FOR THIS REASON WILL KEEP MENTION OF FREEZING DRIZZLE/FOG GENERALLY SOUTH OF I-80 THROUGH THE MORNING HOURS. HOWEVER... LIGHT SNOW POTENTIAL ALONG MID LEVEL FRONTOGENETIC ZONE ACROSS NORTHERN HALF OF CWA STILL LOOKS GOOD. SNOW RATES SHOULD REMAIN RATHER LIGHT SO WILL MENTION ACCUMULATIONS UNDER AN INCH. IT REALLY STARTS TO GET FUN TONIGHT INTO EARLY WEDNESDAY AS DIRECT CIRCULATION ON BACK SIDE OF UPPER JET HELPS PLUNGE STRONG REINFORCING SHOT OF ARCTIC AIR SOUTH ACROSS FA. WITH 850MB TEMPS OF -15 TO -25 ALREADY PRESENT ACROSS THE NORTHERN PLAINS FULLY EXPECT COLDEST AIR OF THE SEASON TO FILTER IN BEHIND THE FRONT TONIGHT INTO WEDNESDAY. WEAK JET COUPLING ALSO PRODUCES AN ENHANCED AREA OF MID LEVEL FRONTOGENESIS STRETCHING FROM NORTHWEST CORNER OF FA TO SOUTHEAST. EXPECT SOME TYPE OF SNOW BANDING TO DEVELOP JUST SOUTH OF THIS FEATURE WITH BEST SHOT OF SNOW ACCUMULATIONS ALONG A KAIA TO KBBW LINE BY 12Z. DOESN'T APPEAR AS THOUGH SNOW AMOUNTS WILL MEET WARNING CRITERIA AT THIS POINT SO WILL HOLD OFF ON ANY WATCH/WARNING. HOWEVER... SNOW ACCUMULATIONS IN THE 3 TO 5 INCH RANGE LOOK POSSIBLE AND DAY CREW WILL HAVE TO EVALUATE FOR ADVISORY POTENTIAL. FRONTOGENESIS THEN WEAKENS BY AFTERNOON ON WEDNESDAY AS UPPER JET COUPLING SHIFTS EAST AS WELL. THIS SHOULD ALLOW SNOW TO TAPER OFF TO SOME FLURRIES BY AFTERNOON. MAIN ISSUE AT HAND FOR WEDNESDAY IS EXTREMELY COLD TEMPERATURES PRESENT WITH HIGH TEMPS BARELY GETTING BACK ABOVE ZERO ACROSS NORTHEAST ZONES. LUCKILY WINDS ARE NOT LOOKING EXTREMELY STRONG SO WIND CHILL VALUES SHOULD REMAIN ABOVE ADVISORY CRITERIA OF -20. IT DOESN'T GET MUCH BETTER THOUGH WEDNESDAY NIGHT AS LOW TEMPS IN THE -10 TO -15 RANGE LOOK POSSIBLE ACROSS NORTH CENTRAL/NORTHEAST ZONES WITH 0 TO 5 BELOW IN THE SOUTHWEST. SURFACE HIGH THEN RIDGES ACROSS FAR EASTERN PORTIONS OF CWA ON THURSDAY. OVERALL NET EFFECT WILL BE TO KEEP COLD AIR DAMMED UP AGAINST MOUNTAINS FOR ANOTHER DAY. THIS WILL RESULT IN SOME WEAK UPGLIDE OVER COLD DOME KEEPING A THREAT OF LIGHT SNOW/FLURRIES THROUGH THE DAY ACROSS ALL BUT FAR EASTERN ZONES. HIGH TEMPS IN THE 5 TO 20 RANGE LOOK GOOD FOR HIGHS. FRIDAY THROUGH MONDAY...NO CHANGES AT THIS TIME. THANKS GLD FOR COORDINATION. .LBF...NONE. AWJ ne AREA FORECAST DISCUSSION-UPDATED NATIONAL WEATHER SERVICE NORTH PLATTE NE 930 AM CST TUE JAN 21 2003 WILL UPDATE ZONES SHORTLY FOR COSMETIC CHANGES AND TO EXTEND MENTION OF PATCHY LIGHT FREEZING ACROSS THE WEST AND SWRN ZONES INTO THE AFTERNOON HOURS. RAOB SOUNDINGS AT H5...AS WELL AS ETA MODEL SOUNDINGS INDICATING SOME DRYING IN THE MID LEVELS THIS AFTERNOON BEFORE COMPLETELY SATURATING OVERNIGHT. WITH MOIST LL PROFILES WARMING TO ABOVE -10C TODAY...LIGHT FREEZING DRIZZLE SHOULD CONTINUE. DRIZZLE REMAINS VERY LIGHT PER CALLS TO SHERIFFS DEPTS ACROSS THE SRN AND SWRN TIER OF COUNTIES...SO WILL FORGO ADVZY AT THIS JUNCTURE AND RE-EVAL NEAR NOONTIME. FARTHER NORTH...LIGHT SNOW CONTINUES. COOP ACCUMULATIONS THIS AM ARE INDICATING 1-2 INCHES ACROSS THE SANDHILLS...MAINLY FROM SHERIDAN SEWD INTO LOGAN COUNTY. ETA MODEL INDICATING WEAK MID LVL FRONTOGENESIS FIELD SHIFTING EWD AFTER NOON TIME...SO SNOW TAPERING OFF TO FLURRIES LOOKS REASONABLE. NOTE...DUE TO IFPS UPGRADE...GRIDS WILL NOT BE UPDATED TILL NEAR NOONTIME. CLB FREEZING DRIZZLE/SNOW EVENT MAIN CHALLENGE. SURFACE ANALYSIS FROM THIS EARLY MORNING SHOWS ARCTIC FRONT BACKING TO THE SOUTHWEST WITH COLD AIR DAMMING UP AGAINST CENTRAL ROCKIES. QUICK SCAN OF RADAR MOSAIC SHOWS A WEAK BUT PERSISTENT SNOW BAND ALONG A KCDR TO KBBW LINE. FURTHER SOUTH WHERE FOG AND STRATUS IS ALREADY PRESENT... A LACK OF SEEDER FEEDER FROM DENDRITIC LAYER HAS RESULTED IN AREAS OF FREEZING DRIZZLE. LATEST MODEL RUNS HAVE INITIALIZED MID AND UPPER LEVEL FEATURES DECENT... BUT BOUNDARY LAYER FEATURES ARE ANOTHER QUESTION. GFS FALSELY INITIALIZED A 1006 MB LOW ACROSS EASTERN COLORADO WITH ETA DOING A TAD BETTER. DESPITE THESE DIFFERENCES MODELS EVOLVE PATTERN SIMILARLY THROUGH 48-60 HOURS. WILL LEAN TOWARDS ETA FOR THIS FORECAST BASED ON SLIGHTLY BETTER INITIALIZATION. BIGGEST PROBLEM FOR TODAY IS FIGURING OUT WHERE LIGHT SNOW/FLURRIES VERSUS FREEZING DRIZZLE EXIST ACROSS FA. 06Z RUC APPEARS TO BE BACKING OFF ON ANY SEEDING FROM DENDRITIC LAYER ACROSS SOUTHWEST ZONES THAT 00Z ETA AND GFS INDICATED WOULD OCCUR. FOR THIS REASON WILL KEEP MENTION OF FREEZING DRIZZLE/FOG GENERALLY SOUTH OF I-80 THROUGH THE MORNING HOURS. HOWEVER... LIGHT SNOW POTENTIAL ALONG MID LEVEL FRONTOGENETIC ZONE ACROSS NORTHERN HALF OF CWA STILL LOOKS GOOD. SNOW RATES SHOULD REMAIN RATHER LIGHT SO WILL MENTION ACCUMULATIONS UNDER AN INCH. IT REALLY STARTS TO GET FUN TONIGHT INTO EARLY WEDNESDAY AS DIRECT CIRCULATION ON BACK SIDE OF UPPER JET HELPS PLUNGE STRONG REINFORCING SHOT OF ARCTIC AIR SOUTH ACROSS FA. WITH 850MB TEMPS OF -15 TO -25 ALREADY PRESENT ACROSS THE NORTHERN PLAINS FULLY EXPECT COLDEST AIR OF THE SEASON TO FILTER IN BEHIND THE FRONT TONIGHT INTO WEDNESDAY. WEAK JET COUPLING ALSO PRODUCES AN ENHANCED AREA OF MID LEVEL FRONTOGENESIS STRETCHING FROM NORTHWEST CORNER OF FA TO SOUTHEAST. EXPECT SOME TYPE OF SNOW BANDING TO DEVELOP JUST SOUTH OF THIS FEATURE WITH BEST SHOT OF SNOW ACCUMULATIONS ALONG A KAIA TO KBBW LINE BY 12Z. DOESN'T APPEAR AS THOUGH SNOW AMOUNTS WILL MEET WARNING CRITERIA AT THIS POINT SO WILL HOLD OFF ON ANY WATCH/WARNING. HOWEVER... SNOW ACCUMULATIONS IN THE 3 TO 5 INCH RANGE LOOK POSSIBLE AND DAY CREW WILL HAVE TO EVALUATE FOR ADVISORY POTENTIAL. FRONTOGENESIS THEN WEAKENS BY AFTERNOON ON WEDNESDAY AS UPPER JET COUPLING SHIFTS EAST AS WELL. THIS SHOULD ALLOW SNOW TO TAPER OFF TO SOME FLURRIES BY AFTERNOON. MAIN ISSUE AT HAND FOR WEDNESDAY IS EXTREMELY COLD TEMPERATURES PRESENT WITH HIGH TEMPS BARELY GETTING BACK ABOVE ZERO ACROSS NORTHEAST ZONES. LUCKILY WINDS ARE NOT LOOKING EXTREMELY STRONG SO WIND CHILL VALUES SHOULD REMAIN ABOVE ADVISORY CRITERIA OF -20. IT DOESN'T GET MUCH BETTER THOUGH WEDNESDAY NIGHT AS LOW TEMPS IN THE -10 TO -15 RANGE LOOK POSSIBLE ACROSS NORTH CENTRAL/NORTHEAST ZONES WITH 0 TO 5 BELOW IN THE SOUTHWEST. SURFACE HIGH THEN RIDGES ACROSS FAR EASTERN PORTIONS OF CWA ON THURSDAY. OVERALL NET EFFECT WILL BE TO KEEP COLD AIR DAMMED UP AGAINST MOUNTAINS FOR ANOTHER DAY. THIS WILL RESULT IN SOME WEAK UPGLIDE OVER COLD DOME KEEPING A THREAT OF LIGHT SNOW/FLURRIES THROUGH THE DAY ACROSS ALL BUT FAR EASTERN ZONES. HIGH TEMPS IN THE 5 TO 20 RANGE LOOK GOOD FOR HIGHS. FRIDAY THROUGH MONDAY...NO CHANGES AT THIS TIME. THANKS GLD FOR COORDINATION. .LBF...NONE. AWJ ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEWPORT/MOREHEAD CITY NC 1015 AM EST TUE JAN 21 2003 WX PATTERN NEXT FEW DAYS TO REALLY KEEP US ON OUR TOES WITH A THREAT OF WINTRY PCPN. FOR TODAY I WILL CONTINUE TO FCST MOSTLY A NUISANCE EVENT THROUGH 00Z THIS EVENING. STILL SOME UNCERTAINTY ON HOW TONIGHTS FORECAST WILL WORK OUT BUT WE HAVE PLENTY OF TIME TO SORT OUT THE LATEST DATA AND ISSUE AN ADVY IF NEED BE. LATEST SFC ANALYSIS PLACES THE COLD FRONT ON ABOUT A SOP-HSE LINE. COLD AIR IS NOT REALLY POURING IN BEHIND THIS FTR BUT IS SLOWLY FILTERING IN FROM THE NE. DEWPOINTS ARE BEGINNING TO DROP INTO THE TEENS AND 20S IN THIS COOLER AIRMASS. THERE IS ALSO SOME SIGNS OF WEAK DAMMING/WEDGE ACROSS THE NE PORTION OF THE STATE. THE BIG QUESTION REMAINS P-TYPE AND AMOUNT AS WEAK WAVES SLIDE ALONG THE SLOWLY SAGGING FRONTAL BNDRY. I THINK KEY TO THIS AFTERNOONS EVENT IS HOW MUCH DRY AIR WORKS INTO THE REGION AND THUS THE DEGREE OF EVAPORATIVE COOLING. INITIAL THOUGHT WAS MAINLY RAIN MIXING WITH SLEET LATE AS COOLER AIR BEGINS TO BECOME ENTRENCHED. HOWEVER...IF ENOUGH EVAP COOLING TAKES PLACE WE COULD SEE MORE FREEZING RAIN OR SLEET. LIMITING FACTOR IS THE AMOUNT OF MOIST AVBL TO SYSTEM. INDIVIDUAL IMPULSES HAVE LITTLE AMPLITUDE AND POTENTIAL FOR STRONG WAA/BACKING FLOW FOR DEEP MOIST WILL BE LIMITED. LATEST RUC QPF VALID THROUGH 00Z THIS EVENING HAD AMOUNTS LESS THAN 1/10 OF AN INCH. NOT SEEING MUCH IN THE WAY OF RETURNS/PCPN INTENSITY IN THE LATEST RADAR MOSAIC WHICH IS SUPPORTIVE OF A LOW QPF EVENT AT LEAST INITIALLY. TONIGHT AS COLDER AIR CONTINUES TO SPREAD SOUTH WE COULD CONTINUE TO HAVE P-TYPE PROBLEMS. THE GFS REALLY PUSHES THE BNDRY S OF THE REGION AND IS VERY DRY IN THE LOW LEVELS AFT 00Z. THE ETA KEEPS THE BNDRY FURTHER N AND IS MUCH MORE GENEROUS WITH LIFT/QPF/WINTRY PCPN POTENTIAL. FOR NOW WILL STAY CLOSE TO CURRENT PROJECTIONS. WILL ADJUST TEMPS N DOWN AND S UP. MARINE: APPEARS NOTEWORTHY CAA TNGT WILL BRING 20-25 KT N WINDS. WILL HOIST SCA FLAGS THIS UPDATE AS WE EMBARK ON THE 12 HR WINDOW. EVEN IF WINDS FALL SHY OF FULL SCA CRIT...SEAS WILL ONLY NEED A LITTLE BOOST TO REACH SIG HGHTS OF 6 FEET. WILL ALSO INCLUDE PSBL GALE FORCE HEADLINE FOR THU NIGHT AS FRIGID AIR BLASTS INTO THE RGN. .MHX...SCA COASTAL WATERS AND SOUNDS. ELARDO/COLBY nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 1010 PM EST TUE JAN 21 2003 LATEST SURFACE ANALYSIS SHOWS BOUNDARY MOVING SOUTH ACROSS SOUTHERN PART OF FORECAST AREA...WHILE KGSP RADAR SHOWS RAIN GENERALLY SOUTH AND EAST OF INTERSTATE 85. BASED ON RADAR TRENDS...LATEST RUC...AND PEAK AT NEW 00Z ETA...WILL REMOVE PRECIP FROM ALL BUT SOUTHERN THREE ZONES. PARTIAL THICKNESSES AND FORECAST SOUNDINGS DO NOT SUPPORT ANY TYPE OF PRECIPITATION OTHER THAN RAIN EVEN WITH THE COLD AIR SPILLING IN ACROSS THE N. TEMPS ARE IN NEED OF ADJUSTMENT IN THAT AREA AS THEY ARE A CATEGORY ABOVE NEIGHBORS AND MODEL GUIDANCE. IN LIGHT OF CLEARING SKY ACROSS N...LOWERING TEMPS LOOKS LIKE BEST COURSE OF ACTION. .GSP... GA...NONE. SC...NONE. NC...NONE. MOORE ...PREVIOUS DISCUSSION ISSUED AT 315 PM... FOR TONITE AND WEDNESDAY...THE MAIN FEATURE FOR OUR FORECAST AREA WILL BE THE COLD FRONT SLIDING SLOWLY SOUTHWARD. KGSP 88-D STILL SHOWS AN EAST-WEST ORIENTED BAND OF RAIN. MODELS TAKE THIS FRONT SOUTH OF OUR REGION LATE TONIGHT...WITH ONLY VERY LIGHT RAINFALL AMOUNTS. TIMING STILL LOOKS GOOD FOR ONE FINAL VORT TO RIDE ALONG THE BOUNDARY THIS EVENING...SO WILL CONTINUE CHANCE POPS OVERNIGHT FOR THE SOUTHERN HALF OF OUR FORECAST AREA. TEMPERATURES ACTUALLY WERE ABLE TO MAKE SOME RECOVERY ACROSS OUR NORTHERN TIER AFTER A BRIEF DIP INTO THE UPPER 30S...BUT MESOSCALE ANALYSIS SHOWS COLDER AND DRIER AIR ATTEMPTING TO INVADE THE AREA. FORECAST SOUNDINGS STILL SHOW POTENTIAL FOR A WINTRY MIX...WHICH WOULD FALL AS RAIN/SNOW NORTH...AND RAIN/SLEET SOUTH. ANY CHANGEOVER IN UPSTATE/NORTHEAST GEORGIA WOULD OCCUR LATER...TOWARD DAYBREAK FOR AREAS BORDERING THE COLUMBIA AND ATLANTA FORECAST OFFICES. OUR ZONES WILL INCLUDE CHANCE OF DRIZZLE/FLURRIES EARLY NORTHERN FOOTHILLS/NORTHWEST PIEDMONT OF NORTH CAROLINA...FLURRIES NORTHERN MOUNTAINS...DRIZZLE/FLURRIES CENTRAL MOUNTAINS...AND A CHANCE OF RAIN/SNOW ACROSS ALL OF THE SOUTHERN TIER COUNTIES OF NORTH CAROLINA. NO ACCUMULATIONS OF ANY WINTRY WEATHER ARE EXPECTED. ATMOSPHERE DRIES OUT SOME EARLY WEDNESDAY...AND COULD NOT RULE OUT SOME LINGERING LIGHT RAIN ACROSS ABBEVILLE/ELBERT GROUP BUT WILL NOT MENTION FOR NOW. PERSISTENT LOW LEVEL MOISTURE AND POST FRONTAL COLD ADVECTION SHOULD INTERACT TO KEEP A BROKEN TO OVERCAST DECK OVER REGION FOR MOST OF THE DAY...WITH MODEST TEMPERATURE CLIMBS. BURRUS WED NGHT THROUGH FRIDAY...A STRONG SHORT WAVE WL CROSS THE CWA EARLY THU MORNING. THIS CHUNK OF THE POLAR VORTEX WL ALSO BE ACCOMPANIED BY A STRONG ARCTIC FRONT. A GOOD SHOT OF DPVA WL ACCOMPANY THE PASSAGE OF THE UPPER LOW...AS LLVL FRONTOGENETICAL FORCING DEVELOPS IS ASSOCIATION WITH THE ARCTIC BNDRY. THE RESULT IS DEEP FORCING AND A RESPONSE IN BOTH THE ETA AND GFS IN THE FORM OF A SATURATED COLUMN...GOOD UVVS AND UP TO A COUPLE TENTHS OF AN INCH OF LIQUID. IN AN AIRMSS THIS COLD...THAT COULD SPELL A QUCIK COUPLE INCHES OF SNOW ACROSS A GOOD BIT OF THE CWA. IN FACT...IT WOULDN/T BE TOO SURPRISING TO SEE A STRIPE OF WINTER STORM CRITERIA SNOW ALONG THE LEADING EDGE OF THE VORT. HPC NOT TOO IMPRESSED W/THIS SYSTEM PER WWE GRAPHICS...SO WON/T QUITE GO THERE YET...BUT WL UP POPS TO LIKELY WED NGHT MTNS AND 50S E. CERTAINLY THE MID SHIFT WL HAVE TO TAKE A LONG HARD LOOK AT WHAT TO DO W/WED NGHT AND THU MORNING. LOWS THIS MORNING IN SRN ONTARIO WERE AROUND 35 BELOW...OVER A LARGE AREA. IT IS THIS AIRMASS WHICH WL INVADE THE CWFA THU. HAVE GONE A FEW DEGREES UNDER MOS...BUT IT MAY BE THAT TEMPERATURES VERIFY EVEN COLDER THAN WHAT WE HAVE PROGGED NOW. AT ANY RATE...WL BE FLIRTING WITH WIND CHILL WARNING CRITERIA THU MORNING...AND ESPECIALLY OVERNIGHT THU. STRONG CAA AND SUBSIDENCE MAY ALSO CREATE A HIGH WND PROBLEM IN THE MTNS AND FOOTHILLS LATE THU. AND FINALLY...AN AIRMASS THIS COLD W/GOOD H8 UPSLOPE SHOULD RESULT IN WINTER STORM CRITERIA SNOW IN THE USUAL UPSLOPE AREAS...AND PERHAPS A LITTLE FARTHER EAST. WL ISSUE AN SPS AS A WINTER STORM OUTLOOK AND ADDRESS ALL THESE CONCERNS. MCAVOY SATURDAY THROUGH TUESDAY... BY SATURDAY... CENTER OF HIGH PRESSURE WILL BE MOVING INTO LOWER MS RIVER VALLEY AND THEREAFTER EXTENDING EASTWARD ACROSS SOUTHEASTERN STATES. THIS PATTERN WILL RESULT IN A PERIOD OF TRANQUIL WEATHER FOR THE CWA. FLOW ALOFT SATURDAY AND EARLY SUNDAY REMAINS NORTHWESTERLY. A SHORT WAVE WILL CROSS CWA ON SATURDAY... BUT DRY AIR MASS PRECLUDES MENTION OF PRECIPITATION AT THIS TIME. HEIGHTS LOWER IN SOUTHCENTRAL U.S.DURING SUNDAY AND THE TREND CONTINUES MONDAY AND TUESDAY. AS A RESULT... FLOW ALOFT BECOMES MORE WESTERLY THEN SOUTHWESTWERLY THUS CUTTING OFF SUPPLY OF COLD AIR. TEMPERATURE MODIFICATION WILL BE WELL UNDERWAY BY THEN. HAVE FOLLOWED CLOSELY THE HPC GUIDANCE TEMPERATURES WHICH TAKES INTO ACCOUNT A COMPARISON OF GFS AND ECMWF OPERATIONAL AND ENSEMBLE RUNS. LEE FCSTID = 44 GSP 36 45 26 29 / 30 20 50 50 AND 40 48 26 30 / 40 20 50 50 CLT 32 43 26 30 / 20 10 50 50 HKY 28 40 22 26 / 10 10 50 50 AVL 27 39 19 22 / 10 10 60 60 sc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 1052 AM EST TUE JAN 21 2003 SURFACE FRONT CONTINUES TO SLIDE SLOWLY SOUTHWARD TOWARD THE SOUTH CAROLINA BORDER; WE HAVE SEEN A TURN TO MORE OF A NORTHERLY WIND ACROSS THE SOUTHERN NORTH CAROLINA FOOTHILLS AND PIEDMONT THIS MORNING. TO THE SOUTH...EVIDENCE OF STRONG DOWNSLOPE WITH A NARROW CLEAR PATCH FROM GREENVILLE SPARTANBURG METRO AREA EAST INTO THE SOUTH CAROLINA PIEDMONT. KGSP 88-D INDICATES BAND OF FRONTAL PRECIP LINGERING MOSTLY ACROSS THE MOUNTAINS...AWAY FROM THE STRONG DOWNSLOPE THAT IS ERODING THE PRECIPITATION SHIELD. MODELS INDICATE ONE MORE WEAK VORTEX WILL RIDE ALONG THE BOUNDARY IN A FAST WESTERLY FLOW. THUS...WITH ABUNDANT MOISTURE IN THE COLUMN...FEEL LIKELY POPS WARRANTED ALL AREAS THIS AFTERNOON...ALTHOUGH AMOUNTS IN UPSTATE AND NORTHEAST GEORGIA WILL BE MORE SIGNIFICANT THAN TO THE NORTH. WIDE RANGE OF TEMPERATURES EXIST PRESENTLY...WITH UPPER 30S IN THE NORTHERN MOUNTAINS AND NORTHWEST PIEDMONT...TO LOWER 60S NORTHEAST GEORGIA. WILL TREND AFTERNOON WORDING FOR SLOWLY FALLING TEMPERATURES ALL NORTH CAROLINA ZONES FOR THE AFTERNOON...WHERE MAXIMA HAVE LIKELY BEEN REACHED ALREADY...BUT WILL RAISE MAXES UPSTATE AND NORTHEAST GEORGIA TO THE VICINITY OF 60F. AS FAR AS PRECIPITATION TYPE...FORECAST RUC SOUNDINGS SUGGEST MOSTLY LIQUID PRECIPITATION FOR THE REST OF THIS PERIOD. EXCEPTIONS ARE ACROSS THE NORTHERN TIER...WITH SOUNDING GOING PREDOMINANTLY SNOW NORTHERN MOUNTAINS...AND RAIN/SNOW MIXTURE FOR THE NORTHERN FOOTHILL AND NORTHWEST PIEDMONT. WILL THROWN IN A TOKEN MENTION OF LIGHT SNOW POSSIBLE FOR THE CENTRAL NORTH CAROLINA MOUNTAINS...ALTHOUGH FORECAST SOUNDINGS SUPPORT ALL RAIN THERE THROUGH THE AFTERNOON. RAIN FOR ALL OF THE SOUTHERN TIER NORTH CAROLINA COUNTIES LOOKS GOOD THROUGH LATE AFTERNOON...AS WELL AS THE MUCH WARMER UPSTATE AND NORTHEAST GEORGIA ZONES. MIXING IN THE PARTLY CLOUDY SOUTHERN THIRD RESULTING IN GUSTY WINDS AGAIN TODAY. WILL BOOST UPSTATE/NORTHEAST GEORGIA WINDS INTO THE 15 TO 25 MPH RANGE FOR THE AFTERNOON...REQUIRING A WIND ADVISORY FOR AREA LAKES. FCSTID = 44 GSP 59 33 40 27 / 40 60 20 30 AND 60 36 43 28 / 40 60 20 30 CLT 52 31 38 24 / 70 50 10 30 HKY 41 29 38 24 / 60 40 10 30 AVL 46 29 37 17 / 60 50 10 40 .GSP... GA...WIND ADVISORY FOR ALL AREA LAKES THIS AFTERNOON. NC...NONE. SC...WIND ADVISORY FOR ALL AREA LAKES THIS AFTERNOON. BURRUS sc AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 1005 AM CST TUE JAN 21 2003 BIG PICTURE THIS MRNG CAPTURES QUICK NW FLOW ALFT ACRS REGION WITH NO SIGNIFICANT IMPULSES TO SLIDE THRU NRN PLAINS. MAIN BAROCLINIC ZONE SOMEWHAT SPLIT IN MID LVLS...ONE THRU NEBRASKA WHICH IS THE MAJOR AND DEEPER ZONE...AND ANOTHER FM NERN MT TO NERN SD. RAOBS ACRS REGION INDICATE FAIRLY DECENT AMTS OF MID LVL MSTR...AND COLD AIR WELL ENTRENCHED WITH SFC RIDGING FM ND INTO ERN NEBRASKA. MAIN ISSUE TODAY IS PROBABLY THE COLD...BUT WL HAVE TO GIVE ATTENTION TO THREAT FOR LIGHT SNOW/FLURRIES. DESPITE LACK OF DEEP QG FORCING...THERE IS SOME MODEST MID LVL FRONTOGENESIS WITH NRN BNDRY...AND RESULT HAS BEEN FAIRLY IMPRESSIVE COVERAGE OF LOW END REFLECTIVITY ON KBIS AND KABR RADAR. HOWEVER... HAS SOME SERIOUS SATURATING TO DO OVR FSD CWA. RUC/ETA DO INDICATE ENOUGH SATURATION POTENTIAL DVLPG NW TO S DURG AFTN AS BNDRY STARTS TO COLLAPSE SLOWLY SWRD. WITH VERY DENDRITIC TMPS THRU DEEP LYR... LKLY TO SEE AT LEAST FLURRIES INTO PARTS OF CWA NOT COVERED BY THAT MENTION NOW...WITH PSBL EXCEPTION OF FAR E/SE. NOT TOO MUCH OF SIGNIFICANCE TO UPDATE...TWEEKS SOMEWHAT TO WND...AND TMPS APPEAR HIGHLY LIKELY BASED ON MIXING POTENTIAL FM 925 HPA ON HIGHER END OF RANGES...WITH TMPS GNRLY -16C TO -18C. UPDATED TEXT ZONES OUT BY 1620Z...AND GRIDS UPDATED ONCE IFPS UPGRADE COMPLETED. SYSTEM LATE TONIGHT AND WEDNESDAY LOOKING LESS THAN IMPRESSIVE ON ERLY LOOK AT 12Z RUNS...WITH BEST OF LOW THREAT FOR SNOW ALG MO RVR. COLDEST WX THUS FAR THIS WINTER NO DOUBT AHEAD IN THE SHORT TERM. .FSD...NONE CHAPMAN sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NASHVILLE TN 620 AM CST TUE JAN 21 2003 LATEST ANALYSIS SHOWING COLD FRONT ON THE MOVE...WITH COLD AIR NOW SINKING WELL INTO NORTHWEST MIDDLE TN. TEMPERATURES DROPPED SOME 4-6 DEGREES THERE LAST HOUR. TEMPS STILL ABOVE FREEZING BUT NOT TO FAR FROM IT. LATEST RADAR SHOWING BACK EDGE OF MAIN PRECIP BAND STAYING JUST AHEAD OF FREEZING LINE...WITH LITTLE IF ANYTHING UPSTREAM. 06Z META AND LATEST RUC MODELS SEEM TO KEEP MAIN PRECIP BAND JUST AHEAD THROUGHOUT THE DAY. POTENTIAL FOR SIGNIFICANT FREEZING PRECIP SEEMINGLY REMAINS LOW. PLAN HOWEVER TO DO A QUICK UPDATE...REWORDING FOR POSSIBILITY OF BRIEF CHANGEOVER BEFORE ENDING. 07 BNA...NONE. tn AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE FORT WORTH TX 950 AM CST TUE JAN 21 2003 PUBLIC FORECAST... WILL UPDATED ZONES AND OTHER RELEASES TO REMOVE MORNING WORDING... AND CLOUD TRENDS ACROSS THE RED RIVER VALLEY. COLD FRONT PUSHING SOUTH OF THE I-20 CORRIDOR AT 1530Z WITH LOW CLOUDS SPREADING INTO THE NORTHERN METROPLEX AREAS. 75 ======================================================> 535 AM CST TUE JAN 21 2003 ...AVIATION DISCUSSION... MAIN CONCERN FOR THIS TAF WILL BE TIMING OF COLD FRONTAL PASSAGE THIS MORNING. SHORT TERM MODEL GUIDANCE FROM THE MESOETA AND RUC 40 BOTH APPEAR TO HAVE A GOOD HANDLE ON CURRENT POSITION OF COLD FRONT...AND ARE CONSISTENT IN BRINGING IT ACROSS DFW AREA 21/14-17Z AND WACO AREA 21/18-21Z. SOUTHWEST WINDS 8-12 KNOTS CURRENTLY WILL VEER TO NORTHWEST AND INCREASE TO 15-20 KNOTS FOLLOWING FROPA. WILL GO AHEAD AND INCLUDE LLWS WORDING IN ALL FOUR TAFS THIS MORNING...AS PRELIMINARY RAOB DATA INDICATES 30+ KNOTS OF SHEAR IN THE SURFACE-1000M AGL LAYER. WILL NOT ADJUST CLOUD FORECAST FROM PREVIOUS TAF...AS IT APPEARS TO BE IN GOOD SHAPE. 65/DD ...PREVIOUS PUBLIC DISCUSSION... COLD FRONT HAS ENTERED SOUTHERN OKLAHOMA DURING THE LATE NIGHT...AND WAS POISED TO ENTER NORTH TEXAS BEFORE DAYBREAK. WINDS WILL SHIFT INTO THE WEST-NORTHWEST PRIOR TO FRONT...WITH COOLING EFFECTS COMING AS WINDS BECOME MORE NORTHERLY. LOW CLOUDS ARE LIKELY TO COME LATER THAN WE THOUGHT 24 HOURS AGO. THEY SHOULD ENTER THE AREA BY LATE AFTERNOON...AND HOLD THROUGH TONIGHT AND WEDNESDAY. A DOSE OF EVEN COLDER TEMPERATURES WILL ARRIVE LATE WEDNESDAY AND EARLY THURSDAY. WE LOWERED TEMPERATURES IN THAT PERIOD...BUT NOT QUITE AS MUCH AS THE NEW GFS GUIDANCE. AS THE WEAKENING BAJA LOW MOVES ACROSS THE AREA...THERE SHOULD BE SUFFICIENT CLOUDINESS TO KEEP TEMPERATURES FROM PLUMMETING AS FAR AS THE GFS FORECASTS FOR THURSDAY MORNING. WE HAVE STRICKEN SLIGHT CHANCE POPS FROM THE SEVEN DAY FORECAST. THE PERSISTENCE OF THE PNA TELECONNECTION (TROUGHING IN THE SOUTHERN ALASKAN AREA WHICH TELECONNECTS TO PERSISTENT TROUGHING IN THE SE U.S.AND UPPER RIDGING IN THE AMERICAN WEST) PROMISES A MOSTLY DRY PATTERN WITH NORTHWEST FLOW ALOFT. WE JUST DON'T FEEL THAT WE HAVE SUFFICIENT EVIDENCE THAT ANY OF THE WEAK NORTHWEST FLOW DISTURBANCES WILL HAVE SUFFICIENT MOISTURE FOR PRODUCING PRECIP. FCSTID = 26 DFW 60 33 44 32 / 0 0 0 0 ACT 69 37 48 32 / 0 0 0 0 PRX 55 32 41 30 / 0 0 0 0 DTO 54 32 42 30 / 0 0 0 0 TKI 54 32 42 30 / 0 0 0 0 DAL 60 34 45 32 / 0 0 0 0 TRL 64 35 42 32 / 0 0 0 0 CRS 70 37 46 34 / 0 0 0 0 TPL 70 40 49 36 / 0 0 0 0 .FWD... TX...NONE. tx COASTAL BEND FORECAST DISCUSSION NATIONAL WEATHER SERVICE CORPUS CHRISTI TX 940 AM CST TUE JAN 21 2003 FOG AND LOW CLOUDS BEGINNING TO LIFT OVER THE REGION AND WILL ALLOW DENSE FOG ADVISORY TO EXPIRE. 12Z SOUNDING SHOWED VERY DRY LAYER JUST ABOVE STRONG SFC INVERSION. 925 MB TEMPS OF 25 DEG C SHOULD HELP MAKE FOR A WARM DAY...BUT LOW CLOUDS AND FOG HAVE ROBBED THE SFC OF A COUPLE HOURS OF DIURNAL HEATING AND PREVIOUS FCST ACCOUNTED FOR THIS...SO TEMPS LOOK ON TRACK. STRONGER WINDS WILL MIX DOWN...HOWEVER PRESSURE GRADIENT WILL WEAKEN THROUGHOUT THE DAY. WILL MAKE SOME MINOR CHANGES TO WIND FCST ON THE UPDATE. FAIR WX CU SHOULD BEGIN TO FORM THIS AFTERNOON AS CONVECTION FROM SFC HEATING TAKES PLACE...BUT DUE TO DRY AIR IN THE LOW LEVELS WILL OPT FOR MOSTLY SUNNY WORDING. MARINE...WINDS AND SEAS HAVE DECREASED AT 42019...42020...AND THE NWS PLATFORM THIS MORNING. WITH RUC...ETA12 AND GFS FORECASTING A LESSER GRADIENT...EXPECT TO REMOVE SCA AND PUT SCEC OUT FOR THE OFFSHORE WATERS. NO UPDATES ELSEWHERE. .CRP...NONE. 92/TR..PUBLIC 72/AP..MARINE tx AREA FORECAST DISCUSSION...UPDATED TO ADD AVIATION DISCUSSION NATIONAL WEATHER SERVICE FORT WORTH TX 535 AM CST TUE JAN 21 2003 ...AVIATION DISCUSSION... MAIN CONCERN FOR THIS TAF WILL BE TIMING OF COLD FRONTAL PASSAGE THIS MORNING. SHORT TERM MODEL GUIDANCE FROM THE MESOETA AND RUC 40 BOTH APPEAR TO HAVE A GOOD HANDLE ON CURRENT POSITION OF COLD FRONT...AND ARE CONSISTENT IN BRINGING IT ACROSS DFW AREA 21/14-17Z AND WACO AREA 21/18-21Z. SOUTHWEST WINDS 8-12 KNOTS CURRENTLY WILL VEER TO NORTHWEST AND INCREASE TO 15-20 KNOTS FOLLOWING FROPA. WILL GO AHEAD AND INCLUDE LLWS WORDING IN ALL FOUR TAFS THIS MORNING...AS PRELIMINARY RAOB DATA INDICATES 30+ KNOTS OF SHEAR IN THE SURFACE-1000M AGL LAYER. WILL NOT ADJUST CLOUD FORECAST FROM PREVIOUS TAF...AS IT APPEARS TO BE IN GOOD SHAPE. 65/DD ...PREVIOUS PUBLIC DISCUSSION... COLD FRONT HAS ENTERED SOUTHERN OKLAHOMA DURING THE LATE NIGHT...AND WAS POISED TO ENTER NORTH TEXAS BEFORE DAYBREAK. WINDS WILL SHIFT INTO THE WEST-NORTHWEST PRIOR TO FRONT...WITH COOLING EFFECTS COMING AS WINDS BECOME MORE NORTHERLY. LOW CLOUDS ARE LIKELY TO COME LATER THAN WE THOUGHT 24 HOURS AGO. THEY SHOULD ENTER THE AREA BY LATE AFTERNOON...AND HOLD THROUGH TONIGHT AND WEDNESDAY. A DOSE OF EVEN COLDER TEMPERATURES WILL ARRIVE LATE WEDNESDAY AND EARLY THURSDAY. WE LOWERED TEMPERATURES IN THAT PERIOD...BUT NOT QUITE AS MUCH AS THE NEW GFS GUIDANCE. AS THE WEAKENING BAJA LOW MOVES ACROSS THE AREA...THERE SHOULD BE SUFFICIENT CLOUDINESS TO KEEP TEMPERATURES FROM PLUMMETING AS FAR AS THE GFS FORECASTS FOR THURSDAY MORNING. WE HAVE STRICKEN SLIGHT CHANCE POPS FROM THE SEVEN DAY FORECAST. THE PERSISTENCE OF THE PNA TELECONNCECTION (TROUGHING IN THE SOUTHERN ALASKAN AREA WHICH TELECONNECTS TO PERSISTENT TROUGHING IN THE SE U.S.AND UPPER RIDGING IN THE AMERICAN WEST) PROMISES A MOSTLY DRY PATTERN WITH NORTHWEST FLOW ALOFT. WE JUST DON'T FEEL THAT WE HAVE SUFFICIENT EVIDENCE THAT ANY OF THE WEAK NORTHWEST FLOW DISTURBANCES WILL HAVE SUFFICIENT MOISTURE FOR PRODUCING PRECIP. FCSTID = 26 DFW 60 33 44 32 / 0 0 0 0 ACT 69 37 48 32 / 0 0 0 0 PRX 55 32 41 30 / 0 0 0 0 DTO 54 32 42 30 / 0 0 0 0 TKI 54 32 42 30 / 0 0 0 0 DAL 60 34 45 32 / 0 0 0 0 TRL 64 35 42 32 / 0 0 0 0 CRS 70 37 46 34 / 0 0 0 0 TPL 70 40 49 36 / 0 0 0 0 .FWD... TX...NONE. tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 825 PM MST TUE JAN 21 2003 SNOWFALL HAS INCREASED OVER EAST CENTRAL WYOMING AND THE FAR NORTHERN NEBRASKA PANHANDLE SINCE 01Z. THAT INCREASE IN SNOWFALL SEEMED TO BE ASSOCIATED WITH AN AREA OF MID LEVEL CONVERGENCE WHICH HAS CAUSED THE ENHANCEMENT ON SATELLITE IMAGERY TO INCREASE FROM KDGW TO KCDR. THE LATEST RUC CONTINUES TO SHOW THE BEST FRONTOGENESIS STAYING MAINLY OVER NORTHEAST WYOMING AND WESTERN SOUTH DAKOTA THROUGH 12Z. SO IT STILL APPEARS THAT THE MAIN AREA FOR SNOW WILL BE IN THE NORTH PART OF THE CWA THE REST OF TONIGHT. ACCUMULATIONS IN THE AREA WERE UP TO 1.5 INCHES LAST NIGHT AND WOULD EXPECT MORE LIKE 2 TO 3 INCHES TONIGHT IN SOME PLACES. THE LIGHT SNOWFALL SHOULD GRADUALLY WORK ITS WAY SOUTH AS THE BAROCLINIC BAND SHOULD EXPAND SOUTH AS THE TEMPERATURES AT 700 MB SLOWLY FALL...PLACING THE MORE FAVORABLE VALUES SOUTH WITH TIME. HOWEVER...THE COLD AIRMASS IS MORE SHALLOW IN THE SOUTHEAST WYOMING PLAINS AND SO EXPECT ONLY A DUSTING. ALONG WITH THE SNOW WILL BE FOG IN MANY PLACES IN THE COLD BOUNDARY LAYER AIR MASS. WEST WINDS AND WARMER TEMPERATURES WILL PERSIST TONIGHT WEST OF THE LARAMIE RANGE. HAVE RECENTLY UPDATED THE FORECAST RECENTLY TO REFLECT THE ABOVE THINKING FOR TONIGHT. .CYS... WY...NONE. NE...NONE. WEILAND wy INTERIOR CENTRAL CALIFORNIA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA 905 PM PST TUE JAN 21 2003 SHORT TERM CONCERN REMAINS POTENTIAL REDEVELOPMENT OF SJ VALLEY INVERSION OVERNIGHT. BAND OF AC TRAVERSING THE CWA HAS DISRUPTED COOLING OF LOWER LEVELS THIS EVE WITH PROFILER DATA SHOWING ONLY SLIGHT WARMING ABOVE 1K FEET. SOUNDINGS ON 00Z ETA/RUC PROJECT DIFFERENT LOW-LEVEL TEMP/DEW POINT STRUCTURES BY 12Z WED WITH RUC MORE FAVORABLE FOR FOG/STRATUS REDEVELOPMENT...AND ETA MAINTAINING CONSIDERABLE DRYING IN LOWER LEVELS. ALTHOUGH RUC APPEARS MORE ON TRACK GIVEN CURRENT VALLEY TEMPS/DEW PTS...INVERSION DEPTH IS NOW PROGGED TO REMAIN AOB 700 FEET THRU 12Z WED WHICH WOULD INHIBIT AREAL COVERAGE. THOUGH 00Z GUIDANCE IS LESS FAVORABLE FOR FOG DEVELOPMENT...IR IMAGERY SHOWS UPSTREAM BREAKS IN CLOUDINESS WHICH MAY RESULT IN FOG FORMATION GIVEN SMALL DEW POINT DEPRESSIONS. GIVEN UNCERTAINTY...WILL MAINTAIN DENSE FOG ADVISORY AT THIS TIME BUT CONT TO MONITOR RATE AT WHICH INVERSION REDEVELOPS. FOR THE MTNS/DESERTS...AFTER CURRENT BAND OF AC SHIFTS EAST WITH TEMPORARY CLEARING...HIGH LEVEL MOISTURE WILL INCREASE LATE TONIGHT AS FRONTAL BAND PRESSES EAST. 00Z ETA/GFS HAVE COME INTO BETTER AGREEMENT AND ARE SIMILAR INDICATING BAND OF MODERATE MID-LEVEL UVM SHIFTING INTO THE CWA WED AFTERNOON...AND CURRENT POPS REMAIN ON TRACK. WILL PREPARE MINOR UPDATE TO TWEAK CLOUD COVER IN THE KERN MTNS... WITH NO OTHER CHANGES AT THIS TIME. .HNX...DENSE FOG ADVISORY FOR THE CENTRAL AND SOUTHERN SAN JOAQUIN VALLEY FROM MIDNIGHT TO 1000 AM WEDNESDAY MORNING. JSN ca AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 345 AM EST WED JAN 22 2003 TRUE ARCTIC AIR TO MOVE INTO THE AREA THIS MORNING. VERY COLD TEMPS TODAY AND TONIGHT...ALONG WITH DECENT WINDS...MEAN WIND CHILL AND LES MAIN FOCUS FOR PERIOD. LATEST WATER VAPOR IMAGES AND UPR AIR ANALYSIS SHOWS A SHARP TROUGH ASSOCIATED WITH ARCTIC AIR MOVING INTO NRN LAKE SUPERIOR....WITH SOME MID LVL MOISTURE IMMEDIATELY BEHIND THE SYSTEM. 850MB TEMPS OVER MANITOBA AND SASKATCHEWAN ARE AROUND -31C...AND THIS ARCTIC VORTEX WILL MOVE OVER THE CWFA LATER THIS AFTN AND THIS EVENING. VERY COLD TEMPS ARE OBSERVED UNDER THE HEART OF THE ARCTIC HIGH PRES IN NRN SASKATCHEWAN...WITH -53F SFC TEMP REPORTED AT CYKJ AT 07Z. THIS ARCTIC HIGH WILL BE NOSING INTO THE NRN PLAINS TODAY...LEADING TO A TIGHTENING PRES GRADIENT BTWN THE HIGH AND THE LAKE INDUCED TROUGH TODAY. CLOSER TO HOME...SOME LES BANDS HAVE SHIFTED INTO EASTERN MQT COUNTY AS SFC WINDS TEMPORARILY VEERED TO A 345 DIR WITH LAKE INDUCED TROUGH TEMPORARILY MOVING SOUTH. THIS WILL LIKELY BE SHORTED LIVED AS THE RUC SUGGESTS WINDS TO BACK TO A 330 DIR THIS MORNING AS THE HIGH PRES MOVES SOUTH...PUSHING THE LES OUT OF MQT COUNTY. REALLY SEE NO REASON WHY LES WILL NOT CONTINUE IN THE NW FAVORED COUNTIES TODAY. HOWEVER...IT WILL PROBABLY BE A LITTLE LESS ORGANIZED ESPECIALLY OVER THE WEST AS H95 CVRG WEAKENS AS THE HIGH PRES OVER MANITOBA/SASKATCHEWAN MOVES INTO THE NRN PLAINS. HOWEVER...STILL PLAN ON GOING ANOTHER 1 TO 4 INCHES OVER THE NW FAVORED SNOWBELT AREAS AS DELTA-T VALUES WILL INCREASE DURING THE DAY DUE TO THE -28C AIR MOVING OVERHEAD. MAIN LIMITING FACTOR IS LOWER INVERSION (AROUND 4000 FEET WEST AND 5500 FEET EAST) WILL DROP THE CURRENT ADVY FOR AREA FOR UPCOMING WARNING ISSUANCE (SEE BELOW FOR DETAILS). TEMPS ARE QUITE TOUGH FOR TODAY. NGMMOS GUIDANCE FOR MQT ACTUALLY HAS TEMPS LOWERING ALL DAY TO -11F BY 00Z. THIS SEEMS A LITTLE TO AGGRESSIVE...ESPECIALLY WITH NWLY WINDS AND THE BIG LAKE JUST TO OUR NORTH. HOWEVER...WITH -28C AT 850MB...WILL PROBABLY SEE SOME SUB-ZERO HIGHS TODAY AND NOT MUCH INCREASE IN TEMPS. AS THE WINDS PICK UP TODAY DUE TO THE TIGHTER PRES GRAD FROM THE BUILDING HIGH OVER THE PLAINS...WIND CHILLS WILL START TO BECOME A FACTOR...ESPECIALLY LATE. TOUGH CALL FOR HEADLINES TONIGHT...AS THERE WILL BE LIKELY MULTIPLE EVENTS GOING ON (LES/WIND CHILL). FIRST FOR THE LES. AS THE MAIN ARCTIC VORTEX MOVES OVERHEAD...MID LVL MOISTURE FILTERS INTO THE AREA (SEEN QUITE WELL OVER HUDSON BY IN IR IMAGERY). IMMEDIATELY BEHIND THE MAIN VORTEX...THERE IS ANOTHER SHEARED S/WV PROGGED BY BOTH MODELS TO MOVE OVERHEAD DURING THE NIGHT. THIS AREA IS ASSOCIATED WITH SOME H85-H5 Q-VECTOR CVRG AND HELPS TO RAISE THE INVERSION TO ABV 5000 FEET FOR A SHORT TIME AROUND MIDNIGHT (INVERSION TO 7000 FEET OVER THE EAST WITH LONGER OVER WATER FETCH). ALTHOUGH DYNAMICS ARE MINIMAL...AND SNOW GROWTH MICROPHYSICS NOT THE BEST...STILL SEE THE POTENTIAL FOR 3 TO 7 INCHES/12 HRS TONIGHT OVER THE WEST...AND 4 TO 8 OVER THE EAST (LONGER FETCH). ALTHOUGH AMTS WILL REALLY BE HIGH ADVY AMTS...FEEL THAT THE COMBO OF STRONG NW WINDS (15-25 MPH NEAR THE SHORELINE) AND WIND CHILLS APPROACHING -25F...FEEL UPGRADE OF WATCHES TO WARNING IS A GOOD CALL. WITH WINDS AROUND 330 DEG TONIGHT...KEWEENAW WILL MISS OUT ON THE BEST SNOWS DUE TO BEING SHADOWED BY ISLE ROYALE. HOWEVER...IT IS VERY POSSIBLE THAT THEY WILL GET SOME LOW VSBYS DUE TO BLSN. THIS ALONG WITH LOW WIND CHILLS THERE (ALTHOUGH PROBABLY NOT AS LOW DUE TO PROXIMITY TO WATER)...WILL ISSUE A WINTER WX ADVY FOR SNOW/BLSN AND LOW WIND CHILLS. WILL GO A 2 TO 5 INCH ACCUM THERE PER LOCAL LES GUIDANCE. EVEN MQT COUNTY COULD SEE SOME LES TONIGHT DESPITE NW FLOW NR THE SFC. WITH 850MB WINDS VEERING TO THE N AFTER 06Z...IT IS POSSIBLE THAT THE NW-SE ORIENTED BANDS WILL ACTUALLY MOVE DUE SOUTH INTO MQT COUNTY. FAR EASTERN MQT COUNTY WILL NEED TO BE WATCHED FOR ADVY LVL SNOWS AS WELL LATER TONIGHT AND THU MORNING...BUT WILL LEAVE THEM OUT OF ANY ADVY SNOWS FOR NOW. NOW FOR THE WIND CHILLS OVER THE INTERIOR. ALL GUIDANCE VALUES FOR IMT/IWD SHOW MINS AROUND -9F TONIGHT...BUT 3HRLY TEMP PROFILES ONLY SHOW TEMPS DIPPING TO AROUND -4 TO -5F. THIS MAKES THE DIFFERENCE IN HAVING WIND CHILL ADVY CRITERIA (-25F) OR NOT. LOOKING AT UPSTREAM AREAS UNDER THE VORTEX...THERE ARE PLACES THAT ARE -15F WITH 15KT OF WIND...SO EVEN WITH THE VORTEX MODERATING A LITTLE...AND WITH SMALL LAKE INFLUENCES...IT IS STILL LIKELY THAT -10F IS NOT OUT OF THE QUESTION AWAY FROM THE LAKE EVEN WITH THE WIND. WITH STRONG PRES GRADIENT BTWN THE LAKE INDUCED TROUGH AND THE ARCTIC HIGH BUILDING INTO THE PLAINS...IT IS HIGHLY UNLIKELY THAT LOW LVL WINDS WILL DECOUPLE OVER INLAND AREAS...SO WIND SPDS OF 10-20 MPH NOT OUT OF THE QUESTION. WILL THEREFORE GO WITH A WIND CHILL ADVY FOR SRN HOUGHTON/MQT/BARAGA/IRON/DICKINSON/MNM COUNTIES (NRN HOUGHTON/ONTONAGON/GOGEBIC/KEWEENAW COUNTIES WILL HAVE LOW WIND CHILLS MENTIONED IN WINTER WX STATEMENT). ULTIMATELY...TEMPS MAY STEADY OFF AFTER MIDNIGHT AS THE COLDEST H85 AIR MOVES TO THE SE OF THE CWFA. HOWEVER...IT IS VERY POSSIBLE BY THAT POINT THE TEMPS WILL HAVE ALREADY DROPPED ENOUGH TO ACHIEVE WIND CHILL ADVY CRITERIA. OVER THE EAST...TEMPS WILL BE MODERATED BY THE LONG FETCH OVER THE LAKE...AND THEY WILL NOT BE UNDER THE COLDEST H85 AIR (IT SLIPS TO THE SOUTH). THEREFORE...TEMPS WILL BE WARMER AND DESPITE WINDS 10-25 MPH...WIND CHILLS SHOULD STAY BLO -25F. OTHERWISE ON THU...WAA FROM THE N SHOULD MARK THE BEGINNING OF THE END OF THIS ROUND OF LES. ETA MUCH MORE AGGRESSIVE THAN THE GFS IN H85 WARMING (BY 5 DEG) DURING THE DAY. THIS IS LIKELY DUE TO INVERSION HEIGHTS...AS BUFR DATA ON BUFKIT SUGGEST INVERSION HEIGHTS LOWERING TO 2500 FEET ON THU (WITH TEMPS AT TOP OF INVERSION STILL AROUND -19C). SO...IT IS UNLIKELY THAT LES WILL STOP COMPLETELY...AND IT MIGHT TAKE LONGER THAN THE ETA SUGGESTS. HOWEVER...IT WILL BE A LITTLE WARMER ON THU...BUT PROBABLY NOT AS MUCH AS THE NGM MOS SHOWS. WILL KEEP TEMPS IN THE UPR SINGLE DIGITS/LOWER TEENS. NO CHANGES PLANNED TO REMAINDER OF FCST. STILL LOOKS LIKE A WARMUP FOR THE BEGINNING OF NEXT WEEK. COORD WITH GRB...DLH AND APX...THANKS. .MQT...WINTER STORM WARNING WED NIGHT INTO THU MORNING MIZ002-006- 007-009-085. WINTER WEATHER ADVY TONIGHT INTO THU MORNING MIZ001-003. WIND CHILL ADVY TONIGHT INTO THU MORNING MIZ004-005-010-011- 012-084. HEAVY FREEZING SPRAY WARNING LAKE SUPERIOR. MRD mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON MS 315 AM CST WED JAN 22 2003 ...ARCTIC AIR STILL ON THE WAY... ALL MODELS CONTINUE TO SHOW EXCELLENT AGREEMENT AND CONTINUITY ON BRINGING CENTER OF ARCTIC HIGH PRESSURE INTO THE LOWER MISSISSIPPI VALLEY REGION BY FRIDAY MORNING. INTRUSION OF THE ARCTIC AIR WILL BE ACCOMPANIED BY LOW WIND CHILL READINGS THURSDAY AND VERY COLD OVERNIGHT LOW TEMPERATURES THURSDAY NIGHT AND FRIDAY NIGHT. IN THE SHORTER TERM...FORECAST CONCERNS WILL CENTER ON RAIN AND THUNDERSTORM CHANCES ASSOCIATED WITH POLAR FRONT CURRENTLY SAGGING SOUTHWARD ACROSS THE FORECAST AREA. LATEST SATELLITE IMAGERY AND RUC ANALYSIS DEPICT NICELY A SHORTWAVE TROUGH TRAVERSING THE FORECAST AREA. DESPITE CONFLUENT FLOW ALOFT...DAMPENING WAVE WAS ENOUGH TO TRIGGER SHOWER/TSTM COMPLEX IN STRONG E-W BAROCLINIC ZONE. MOST ACTIVITY IS CONFINED ALONG HWY 82 CORRIDOR IN REGION OF STRONGEST UPGLIDE AND ASCENT. WITH SHORTWAVE PROGRESSING STEADILY EASTWARD...EXPECT THAT ORGANIZED CONVECTION WILL MOVE OUT BEFORE SUNRISE. FOR NOW...PLAN TO MENTION LIGHT RAIN/DRIZZLE IN CNTRL/SRN ZONES ASSOC WITH POST-FRONTAL COLD ADVECTION AND LOW LEVEL MOISTURE. OTHERWISE...SHOULD SEE A GRADUAL DECREASE IN CLOUDS FROM N TO S AS FRONT CONTINUES SWD PROGRESSION. TEMPS COULD BE A LITTLE TRICKY WHERE SUN COMES OUT. FOR NOW WILL STICK CLOSE TO ETA 2M TEMPS...EXCEPT A COUPLE OF DEGREES COOLER THAN ETA IN SRN ZONES WHERE NO SUN EXPECTED. CURRENTLY...CENTER OF 1055MB ARCTIC HIGH OVER NRN CANADA IS BEGINNING TO SLIP SOUTHWARD IN RESPONSE TO INTENSIFYING JET STREAK THAT IS FORECAST TO DRAG ARCTIC STREAM DEEP INTO SOUTHEAST US. CURRENT TEMPS ARE AS COLD AS -51 F OVER NRN SASKATCHEWAN. PAST SEVERAL RUNS OF THE UKMET/GFS/ETA HAVE BROUGHT THE HIGH CENTER TO NEAR KANSAS CITY BY THURSDAY EVENING (~1042MB). FROM THEIR...MODELS BRING CENTER OF HIGH RIGHT OVER THE FORECAST AREA FRIDAY NIGHT. THINKING RIGHT NOW IS THAT START OF STRONGEST COLD ADVECTION SHOULD BEGIN WEDNESDAY EVENING AND PERSIST INTO THURSDAY EVENING. DURING THIS TIME...A TIGHT PRESSURE GRADIENT WILL EXIST AND KEEP SURFACE WINDS IN FROM 10 TO 25 MPH. WITH AREA TEMPERATURES VARYING FROM THE UPPER TEENS TO MID 30S DURING THIS PERIOD...WIND CHILLS WILL RANGE FROM NEAR ZERO TO THE MID 20S. CONCERNING TEMPERATURES...RECENT EXPERIENCES INDICATE THAT MAV GUIDANCE IS TYPICALLY A LITTLE TOO COLD IN COLD OUTBREAKS. CONSIDERING THIS AND THAT ARCTIC AIRMASSES ARE NOT GOOD RADIATORS...WILL BUMP MAV TEMPS UP ~4-8 DEGREES ACROSS THE BOARD. PLAN TO MENTION SINGLE DIGIT LOW TEMPS OVER NC/NE ZONES...AROUND 10 CNTRL/NW ZONES...TO AROUND 15 ELSEWHERE FOR THURSDAY NIGHT. ALTHOUGH AIRMASS WILL MODIFY A BIT...DO NOT EXPECT MUCH RECOVERY OF TEMPS FRIDAY WITH HIGH CENTER OVER AREA. LOOKS LIKE SRN STREAM WILL BE A LITTLE MORE ACTIVE RESULTING IN SOME HIGH CLOUD COVER FRIDAY NIGHT. ON THAT NOTE...WILL KEEP SAT MORNING LOWS A WARMER THAN OTHERWISE WOULD BE EXPECTED WITH FAVORABLE POSITION OF SFC HIGH. FORECAST CONFIDENCE LESSENS OVER THE WEEKEND. EXPECT MODERATING TEMPERATURES BEGINNING SAT AFTN...BUT NOT SURE WHAT TO EXPECT WITH INCREASINGLY ACTIVE SRN STREAM. PAST SEVERAL RUNS OF THE UKMET HAVE HINTED AT DEVELOPMENT IN SRN STREAM WITH SIGNALS OF WRN/CNTRL GULF CYCLOGENESIS ~MONDAY. NOW GFS HAS SIMILAR SIGNALS...ALTHOUGH SFC REFLECTION IS MORE SUPPRESSED TO THE SOUTH WITH SHORTWAVE TROUGH MORE SHEARED. MODELS DO SEEM TO BE IN AGREEMENT ON SENDING ONE MORE SHOT OF ARCTIC AIR INTO ERN US. THE EXTENT OF ADVECTION INTO THE LOWER MS VALLEY AND THE INTERACTION WITH ANY SRN STREAM ENERGY WILL BE FOCUS FOR FUTURE FORECASTS. AT THIS POINT...WILL CONTINUE TO LEAVE EXTENDED DRY UNTIL BETTER CONSENSUS CAN BE REACHED. PRELIM NUMBERS... JAN 48/22/35/11 21-- MEI 50/21/35/09 31-- .JAN... AR...NONE. LA...NONE. MS...NONE. 43 ms SOUTH CENTRAL NEBRASKA/NORTH CENTRAL KANSAS FORECAST DISCUSSION NATIONAL WEATHER SERVICE HASTINGS NE 343 AM CST WED JAN 22 2003 ...MAIN FORECAST CONCERN IS LIGHT SNOW/AMOUNTS TODAY... UPPER AIR ANALYSIS SUITE AND WATER VAPOR IMAGERY SHOWING ELONGATED LARGE SCALE THROUGH ENCOMPASSING MUCH OF EASTERN NORTH AMERICA... WITH HEART OF COLD VORTEX STRETCHING FROM SASKATCHEWAN TO QUEBEC AS MAIN CORE /ACARS INDICATED 130KTS/ OF WESTERLIES ARCS THROUGH THE NORTHERN TIER OF STATES. TO THE WEST...UPPER RIDGING PREVALENT FROM ALONG THE PACIFIC WEST COAST INTO ALASKA...WHILE SEVERAL IMPULSES SLIDE THROUGH THE RELATIVELY WEAK FLOW FROM THE FOUR CORNERS AREA TO THE SOUTHERN PLAINS. LATEST SUBJECTIVE SURFACE ANALYSIS FEATURING FRONTAL BOUNDARY ALONG THE ROCKIES OF WYOMING AND COLORADO...WITH ASSOCIATED LOW PRESSURE RIPPLE CENTERED ALONG THE WY/CO BORDER. HIGH PRESSURE RIDGE AXIS EXTENDING FROM WESTERN CANADA INTO THE DAKOTAS...WITH E/NE LOW LEVEL FLOW ENCOMPASSING THE CENTRAL PLAINS. LIGHT SNOW CONTINUES TO SLIDE EASTWARD THROUGH NORTHERN/CENTRAL NEBRASKA EARLY THIS MORNING...AIDED BY MID LEVEL FRONTOGENETICAL FORCING /ROUGHLY IN 800MB-600MB LAYER/ AND COUPLED UPPER JET STRUCTURE. BEST NET LIFT COINCIDENT WITH FAVORABLE DENDRITIC GROWTH EXPECTED TO PERSIST AT LEAST UNTIL MIDDAY...WITH SNOW LIKELY TAPERING OFF AND/OR TO FLURRIES IN THE AFTERNOON. GIVEN EARLY MORNING TREND AND ETA/RUC DIAGNOSTICS...BEST SNOWFALL PROSPECTS STILL APPEAR ROUGHLY FROM THE TRI-CITIES AND AREAS NORTH AND EAST. ONE TO TWO INCH AMOUNTS SHOULD SUFFICE IN THE AFOREMENTIONED AREAS...ALTHOUGH PROBABLY NOT OUT OF THE QUESTION TO SEE ISOLD POCKET OF THREE INCHES. SNOW AMOUNTS ARE EXPECTED TO TAIL OFF MARKEDLY THROUGH THE SOUTHWEST CWA...WHERE LITTLE IN THE WAY OF SNOW ACCUMULATION IS EXPECTED. GIVEN EXPECTED SNOW AMOUNTS GENERALLY IN THE ONE TO TWO INCH RANGE AND ABSENCE OF ADDITIONAL NUSSIANCE FACTORS -- STRONG WINDS FOR INSTANCE -- WILL NOT ISSUE ADVISORY FOR THE NORTH/EAST CWA UNLESS PRE-ISSUANCE TRENDS/REPORTS DICTATE OTHERWISE. WITH ENDING OF SNOW THIS AFTERNOON/EARLY EVENING...QUESTION TURNS TO EVENTUAL POSITIONING OF LOW CLOUDS TONIGHT -- AND SUBSEQUENT IMPACTS ON LOW TEMPERATURES -- AS 1044MB HIGH PRESSURE DEVELOPS SOUTHWARD THROUGH THE NORTHERN PLAINS. 00Z ETA GUIDANCE WOULD SUGGEST AMPLE CLEARING THROUGH THE EASTERN CWA...WITH UPSLOPE TRAJECTORIES MAINTAINING CLOUD COVER FROM THE WESTERN CWA WESTWARD INTO THE HIGHER TERRAIN. IN CONTRAST...00Z GFS PORTRAYS A MUCH MORE CLOUD-PESSIMISTIC SCENARIO. A VERY TOUGH CALL AT THIS TIME AS VERY EASY FOR MOISTURE TO BECOME TRAPPED UNDERNEATH THE RIDGE IN PRESENCE OF WEAKENING AMBIENT LOW LEVEL FLOW...BUT EITHER WAY...CLOUDS OR NOT...A VERY COLD NIGHT IN STORE. SINGLE DIGITS BELOW ZERO...AT LEAST...ARE A SAFE BET FOR MUCH OF THE CWA. IF CLEARING MATERIALIZES IN THE EAST/NORTH CWA TONIGHT...AND GIVEN ADDITIONAL BOUT OF SNOW TODAY...THESE AREAS COULD SEE TEMPERATURES EVEN DIP AS LOW AS 10 TO 15 BELOW ZERO. OTHERWISE... WOULD THINK LIGHT WINDS ASSOCIATED WITH THE RIDGE AXIS WILL PROBABLY NEGATE NECESSITY FOR WIND CHILL HEADLINE...NEVERTHELESS WILL STILL NEED TO BE CLOSELY EVALUATED BY NEXT SHIFT. SURFACE HIGH TO GRADUALLY SLIDE SOUTH/EASTWARD DURING THE DAY ON THURSDAY...WITH SOUTHERLY FLOW DEVELOPING THURSDAY NIGHT INTO FRIDAY. AS SUCH...SHOULD SEE A DECENT TEMPERATURE REBOUND DURING THE DAY ON FRIDAY. WILL MAINTAIN LIGHT SNOW CHANCES THURSDAY NIGHT IN PRESENCE OF LOW TO MID LEVEL WAA/THETA-E ADVECTION REGIME ASSOCIATED WITH PASSING MID LEVEL SHORTWAVE TROUGH. IN THE EXTENDED...REMNANT COLD VORTEX ACROSS WESTERN CANADIAN STILL EXPECTED TO PIVOT TOWARD EASTERN CANADA THIS WEEKEND. THIS WILL BRING A REINFORCING SHOT OF COLDER AIR AND POSSIBLY A SLIGHT SNOW CHANCE SOMEWHERE IN THE SATURDAY TIMEFRAME. PATTERN CERTAINLY LOOKS TO TURN MILDER/DRY BY EARLY NEXT WEEK WITH LOW AMPLITUDE/NEARLY ZONAL FLOW DEVELOPING FROM THE EASTERN PACIFIC THROUGH THE WESTERN CONUS. GOING FORECAST HAS THE AFOREMENTIONED IDEAS WELL IN HAND...THUS ANY OUTER PERIOD ADJUSTMENTS WILL BE MINIMAL. COORDINATED WITH OAX. .GID...NONE. GUYER ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE AMARILLO TX 251 AM CST WED JAN 22 2003 COLD SURFACE RIDGING EXPECTED TODAY. PATCHY FOG IS THE MAIN CONCERN THIS MORNING FOLLOWED BY TEMPS THIS AFTERNOON. MORNING FOG SHOULD BE CONFINED TO WESTERN AND CENTRAL ZONES WHERE LATEST RUC MODEL SHOWS CONTINUED UPGLIDE THROUGH MID MORNING. SUNSHINE THIS AFTERNOON SHOULD BE FILTERED BY MID/HIGH LEVEL CLOUDINESS BUT STILL EXPECT TO REACH 40 OVER THE SOUTHWEST ZONES. SEASONABLY COLD TONIGHT WITH LOWS IN THE SINGLE DIGITS NORTH...MID TEENS SOUTH. COLD 1040 HIGH SETTLES OVER NORTHWEST OK THURSDAY. MODELS TRY TO DEVELOP WEAK LEE TROUGH THURSDAY NIGHT INTO FRIDAY. WINDS MAY REACH 20-25 MPH THURSDAY NIGHT AS MINOR MID LEVEL WAVE APPROACHES FROM THE WEST. WARMING TREND EXPECTED LATER IN THE WEEK. GFS SUPPORTS ANOTHER SHORTWAVE/COLD FRONT SATURDAY NIGHT. BRISK WESTERLY MID LEVEL FLOW EXPECTED MONDAY AND TUESDAY. FCSTID = 13 AMARILLO 40 14 33 20 / 00 00 00 00 BEAVER 32 10 28 13 / 00 00 00 00 BOISE CITY 35 10 29 14 / 00 00 00 00 BORGER 38 12 33 21 / 00 00 00 00 BOYS RANCH 40 13 33 18 / 00 00 00 00 CANYON 42 15 34 21 / 00 00 00 00 CLARENDON 41 14 34 22 / 00 00 00 00 DALHART 38 11 31 16 / 00 00 00 00 GUYMON 33 09 29 15 / 00 00 00 00 HEREFORD 43 16 35 21 / 00 00 00 00 LIPSCOMB 34 10 29 16 / 00 00 00 00 SHAMROCK 39 13 32 21 / 00 00 00 00 WELLINGTON 40 14 33 21 / 00 00 00 00 .AMA... TX...NONE. OK...NONE. $$ tx SOUTH CENTRAL AND SOUTHEAST COLORADO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PUEBLO 415 AM MST WED JAN 22 2003 SHORT TERM DISCUSSION...(TODAY/TONIGHT) ...MAIN CHALLENGES TODAY ARE FOG AND TEMPS... LATEST PRESSURE ANALYSES INDICATES NEXT PUSH OF ARCTIC AIR IS ALREADY PUSHING INTO NORTHEAST COLORADO...WITH 3-HOUR PRESSURE RISES INDICATED FROM THE PALMER DIVIDE NORTHWARD...AND SURFACE OBS INDICATING NORTHEAST WINDS/FALLING DEWPOINTS ACROSS THE NORTHEAST COLORADO PLAINS. SHORT TERM MODELS INDICATE ARCTIC AIR WILL CONTINUE TO MAKE A PUSH INTO THE REGION TODAY AND TONIGHT...ESPECIALLY FROM AFTERNOON INTO THE EVENING ACROSS THE SOUTHEAST COLORADO PLAINS. TEMPS MIGHT TRY TO RECOVER SOME THIS MORNING...BEFORE A SOLID PUSH OF ARCTIC AIR KICKS IN THIS AFTERNOON...BUT REALLY DON'T THINK THEY WILL HAVE TOO MUCH SUCCESS...SAVE FOR THE RIDGES AND PLAINS IMMEDIATELY ADJACENT TO THE MOUNTAINS...INCLUDING THE PALMER RIDGE AND THE SOUTHERN FOOTHILL LOCATIONS. THESE AREAS COULD SEE A QUICK SPIKE IN TEMPS THIS MORNING (MUCH LIKE YESTERDAY)...CLIMBING TO NEAR SEASONAL AVERAGES BEFORE A STRONGER PUSH OF ARCTIC AIR MOVES IN THIS AFTERNOON. SO FAR...FOG IS IN PLACE THROUGH LOWER ARKANSAS RIVER VALLEY TO ABOUT LA JUNTA OR SO...AND IT MAY THREATEN UP PUB WAY AGAIN A LITTLE LATER THIS MORNING. BY AFTERNOON...PROBABLY JUST PARTLY CLOUDY/MOSTLY SUNNY I-25 CORRIDOR...WITH PERSISTENT LOW CLOUDS/FOG FURTHER EAST...HANGING ON THROUGH THE DAY EAST OF LA JUNTA. MAY SEE A RESURGENCE OF LOW CLOUDS ALL THE WAY UP TO THE MOUNTAINS LATE THIS AFTERNOON AS ARCTIC AIR ADVANCES...AND SHALLOW COLD UPSLOPE FLOW LIFTS AIR TO SATURATION. SMALL SNOW SHOWER CHANCES CENTRAL/SOUTHWEST MOUNTAINS STILL LOOKS GOOD TODAY/TONIGHT...AND VERY LOW POPS EASTERN PLAINS FOR LIGHT SNOW SHOWERS TONIGHT STILL LOOKS GOOD AS WELL...WITH THICKER ARCTIC AIR IN PLACE. WILL ALSO ADD SOME FOG FOR THE EASTERN PLAINS AGAIN TONIGHT AS BOTH THE RUC AND MESO-ETA INDICATE IT WILL RETURN. /LW LONG TERM DISCUSSION...(THURS-TUES). THURS/FRI...EXPECT SOME CLOUDS TO MOVE OVER THE AREA THURSDAY. LEFT VERY NEAR ADJACENT MTN PLAINS WARMER...BUT LEFT REST COOLER CONSIDERING CLOUDINESS. AIRMASS FINALLY LOOKS TO PUSH OUT FRIDAY AS SUBSIDENCE BEHIND THURSDAY SHORTWAVE MOVES IN. THIS BRINGS AN INITIAL NW FLOW...THEN SOME COOL UPSLOPE. ONLY TWEAKED SOME TEMPS NEAR MTNS HERE. FAR E PLAINS SHOULD FINALLY SEE A LITTLE RECOVERY FROM THE 30S STARTING FRIDAY WITH HIGHS IN THE 40S AS SKIES CLEAR. SAT/SUN...VERY EARLY SATURDAY S/W MOVING INTO WESTERN COLORADO. BROUGHT POPS IN 6 HRS EARLIER FOR MORE PROGRESSIVE SOLUTION. AVN DROPS ENERGY WEST AND SOUTH INTO THE TROF...WHICH WOULD HELP USHER IN THE COLD 1038 MB AIRMASS BEHIND. WITH THIS RUN 6-12 HRS FASTER THAN THE LAST...HIGHS SATURDAY IN CURRENT SCENARIO WILL BE QUITE COLD AND WOULD DROP AS THE DAY PROGRESSED. SUNDAY LEE TROF PLUS WEAK S/W RIDGING MOVE OVER...PUSHING COLD AIRMASS EASTWARD. MONDAY/TUESDAY...FLOW FLATTENS OVERHEAD TO MORE WESTERLY AS NEXT SYSTEM MOVES INTO THE GREAT LAKES. COOLED TEMPS ABOUT 5F TO BRING PLAINS DOWN TO 50S. COULD PROBABLY ADD ISOLD POPS W AND CNTRL MTNS FOR TUES...WILL LEAVE AS IS FOR NOW AND SEE HOW PATTERN PROGRESSES. .PUB...NONE. co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 1039 AM EST WED JAN 22 2003 THE MAIN CONCERN WITH THIS UPDATE FORECAST IS CHANCE OF SNOW AND TEMPERATURES FOR TODAY...AND THE ON SET OF THE WINTER WEATHER CONDITION TONIGHT. WV IMAGERY AND RUC SHOWING A DEEP LOW OFF THE CANADIAN MARITIME...WITH A ELONGATED SHORTWAVE STRETCHING FROM THIS LOW WEST TO JUST NORTH OF THE GREAT LAKES. SHORTWAVE IMPULSES WRAPPING AROUND THIS LOW WILL GRADUALLY SETTLE SOUTHWARD INTO THE FORECAST AREA TODAY. SURFACE ANALYSIS INDICATE A BROAD RIDGE IS EXPANDING SOUTHEASTWARD FROM THE CANADIAN PRAIRIES. ANTI-CYCLONIC FLOW AROUND THIS RIDGE IS DRAWING COLD ARCTIC AIR FROM CENTRAL CANADA INTO THE FORECAST AREA. WATER-850MB DELTA-T'S CONTINUE TO BE AROUND 28C. THIS IS VERY DRY. THE MORNING RAOBS SHOWING PRECIPITABLE WATER AROUND .05 INCH. RUC/ETA DEPICTING LOW LEVEL (950MB) CONVERGENCE TAKING PLACE ALONG THE LAKE SHORE...FOCUSED AROUND ONTONAGON. CONVERGENCE WILL BECOME WEAKER AROUND NOON...THEN INTENSITY INTO TWO AREAS THIS AFTERNOON... ONE OVER ONTONAGON AND THE OTHER OVER MUNISING AREA. SOUNDINGS INDICATE LOWEST INVERSION IS AROUND 3K FEET OVER THE WEST AND AROUND 4200 FEET OVER THE EASTERN U.P. COLD AIR ADVECTION WILL CAUSE THE INVERSION TO RISE OVER THE FORECAST AREA. SHORTWAVE ENERGY WILL INCREASE OVER LAKE SUPERIOR. VISUAL SATELLITE SHOWING HEAVIEST LAKE EFFECT SNOW BANDS OVER EASTERN LAKE SUPERIOR...WHICH VERIFIES THE MODELS FAIRLY WELL. LAKE EFFECTS SNOW WILL CONTINUE THROUGH THE AFTERNOON...MAINLY OVER THE EASTERN U.P. AND ALONG THE SPINE OF THE KEWEENAW PENINSULA. THE HEAVIEST AMOUNTS WILL STILL BE OVER THE EASTERN COUNTY WARNING AREA. DRY CONDITIONS WILL LIMIT ACCUMULATION. THE COLD AIR MASS ADVECTING OVER THE WARMER TEMPERATURES OF LAKE SUPERIOR WILL ENHANCE THE MIXING TO SURFACE OF SOME OF THE LOW LEVEL JET. THUS WINDS WILL BE HIGHEST ALONG THE LAKE SUPERIOR AND ALONG THE SHORE. WIND CHILLS ARE RUNNING -15C TO -25C ACROSS MUCH OF THE U.P. WINDS WILL ONLY PICK UP A LITTLE. LAKE EFFECT ENDUCED CLOUDS OVER THE NORTHERN U.P. WILL BLANKET THE AREA AND LIMIT SOLAR HEATING. TRAJECTORY FORECAST INDICATING AIR MASS OVER WESTERN ONTARIO YESTERDAY WILL BE OVER THE FORECAST AREA TODAY. THIS AIR MASS WILL BECOME MODIFIED BY THE 34F DEGREE WATERS TEMPERATURES. WILL TRY TO DETERMINE HOW MUCH MODIFICATION WILL BE INVOLVED. THE STRONG WINDS AND COLD TEMPERATURES WILL KEEP JUSTIFY THE NEED FOR FREEZING SPRAY WARNING FOR OVER THE LAKE TODAY. DLG TONIGHT AND LATER... TOUGH CALL FOR HEADLINES TONIGHT...AS THERE WILL BE LIKELY MULTIPLE EVENTS GOING ON (LES/WIND CHILL). FIRST FOR THE LES. AS THE MAIN ARCTIC VORTEX MOVES OVERHEAD...MID LVL MOISTURE FILTERS INTO THE AREA (SEEN QUITE WELL OVER HUDSON BY IN IR IMAGERY). IMMEDIATELY BEHIND THE MAIN VORTEX...THERE IS ANOTHER SHEARED S/WV PROGGED BY BOTH MODELS TO MOVE OVERHEAD DURING THE NIGHT. THIS AREA IS ASSOCIATED WITH SOME H85-H5 Q-VECTOR CVRG AND HELPS TO RAISE THE INVERSION TO ABV 5000 FEET FOR A SHORT TIME AROUND MIDNIGHT (INVERSION TO 7000 FEET OVER THE EAST WITH LONGER OVER WATER FETCH). ALTHOUGH DYNAMICS ARE MINIMAL...AND SNOW GROWTH MICROPHYSICS NOT THE BEST...STILL SEE THE POTENTIAL FOR 3 TO 7 INCHES/12 HRS TONIGHT OVER THE WEST...AND 4 TO 8 OVER THE EAST (LONGER FETCH). ALTHOUGH AMTS WILL REALLY BE HIGH ADVY AMTS...FEEL THAT THE COMBO OF STRONG NW WINDS (15-25 MPH NEAR THE SHORELINE) AND WIND CHILLS APPROACHING -25F...FEEL UPGRADE OF WATCHES TO WARNING IS A GOOD CALL. WITH WINDS AROUND 330 DEG TONIGHT...KEWEENAW WILL MISS OUT ON THE BEST SNOWS DUE TO BEING SHADOWED BY ISLE ROYALE. HOWEVER...IT IS VERY POSSIBLE THAT THEY WILL GET SOME LOW VSBYS DUE TO BLSN. THIS ALONG WITH LOW WIND CHILLS THERE (ALTHOUGH PROBABLY NOT AS LOW DUE TO PROXIMITY TO WATER)...WILL ISSUE A WINTER WX ADVY FOR SNOW/BLSN AND LOW WIND CHILLS. WILL GO A 2 TO 5 INCH ACCUM THERE PER LOCAL LES GUIDANCE. EVEN MQT COUNTY COULD SEE SOME LES TONIGHT DESPITE NW FLOW NR THE SFC. WITH 850MB WINDS VEERING TO THE N AFTER 06Z...IT IS POSSIBLE THAT THE NW-SE ORIENTED BANDS WILL ACTUALLY MOVE DUE SOUTH INTO MQT COUNTY. FAR EASTERN MQT COUNTY WILL NEED TO BE WATCHED FOR ADVY LVL SNOWS AS WELL LATER TONIGHT AND THU MORNING...BUT WILL LEAVE THEM OUT OF ANY ADVY SNOWS FOR NOW. NOW FOR THE WIND CHILLS OVER THE INTERIOR. ALL GUIDANCE VALUES FOR IMT/IWD SHOW MINS AROUND -9F TONIGHT...BUT 3HRLY TEMP PROFILES ONLY SHOW TEMPS DIPPING TO AROUND -4 TO -5F. THIS MAKES THE DIFFERENCE IN HAVING WIND CHILL ADVY CRITERIA (-25F) OR NOT. LOOKING AT UPSTREAM AREAS UNDER THE VORTEX...THERE ARE PLACES THAT ARE -15F WITH 15KT OF WIND...SO EVEN WITH THE VORTEX MODERATING A LITTLE...AND WITH SMALL LAKE INFLUENCES...IT IS STILL LIKELY THAT -10F IS NOT OUT OF THE QUESTION AWAY FROM THE LAKE EVEN WITH THE WIND. WITH STRONG PRES GRADIENT BTWN THE LAKE INDUCED TROUGH AND THE ARCTIC HIGH BUILDING INTO THE PLAINS...IT IS HIGHLY UNLIKELY THAT LOW LVL WINDS WILL DECOUPLE OVER INLAND AREAS...SO WIND SPDS OF 10-20 MPH NOT OUT OF THE QUESTION. WILL THEREFORE GO WITH A WIND CHILL ADVY FOR SRN HOUGHTON/MQT/BARAGA/IRON/DICKINSON/MNM COUNTIES (NRN HOUGHTON/ONTONAGON/GOGEBIC/KEWEENAW COUNTIES WILL HAVE LOW WIND CHILLS MENTIONED IN WINTER WX STATEMENT). ULTIMATELY...TEMPS MAY STEADY OFF AFTER MIDNIGHT AS THE COLDEST H85 AIR MOVES TO THE SE OF THE CWFA. HOWEVER...IT IS VERY POSSIBLE BY THAT POINT THE TEMPS WILL HAVE ALREADY DROPPED ENOUGH TO ACHIEVE WIND CHILL ADVY CRITERIA. OVER THE EAST...TEMPS WILL BE MODERATED BY THE LONG FETCH OVER THE LAKE...AND THEY WILL NOT BE UNDER THE COLDEST H85 AIR (IT SLIPS TO THE SOUTH). THEREFORE...TEMPS WILL BE WARMER AND DESPITE WINDS 10-25 MPH...WIND CHILLS SHOULD STAY BLO -25F. OTHERWISE ON THU...WAA FROM THE N SHOULD MARK THE BEGINNING OF THE END OF THIS ROUND OF LES. ETA MUCH MORE AGGRESSIVE THAN THE GFS IN H85 WARMING (BY 5 DEG) DURING THE DAY. THIS IS LIKELY DUE TO INVERSION HEIGHTS...AS BUFR DATA ON BUFKIT SUGGEST INVERSION HEIGHTS LOWERING TO 2500 FEET ON THU (WITH TEMPS AT TOP OF INVERSION STILL AROUND -19C). SO...IT IS UNLIKELY THAT LES WILL STOP COMPLETELY...AND IT MIGHT TAKE LONGER THAN THE ETA SUGGESTS. HOWEVER...IT WILL BE A LITTLE WARMER ON THU...BUT PROBABLY NOT AS MUCH AS THE NGM MOS SHOWS. WILL KEEP TEMPS IN THE UPR SINGLE DIGITS/LOWER TEENS. NO CHANGES PLANNED TO REMAINDER OF FCST. STILL LOOKS LIKE A WARMUP FOR THE BEGINNING OF NEXT WEEK. .MQT...WINTER STORM WARNING WED NIGHT INTO THU MORNING MIZ002-006- 007-009-085. WINTER WEATHER ADVY TONIGHT INTO THU MORNING MIZ001-003. WIND CHILL ADVY TONIGHT INTO THU MORNING MIZ004-005-010-011- 012-084. HEAVY FREEZING SPRAY WARNING LAKE SUPERIOR. MRD mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1030 AM CST WED JAN 22 2003 DECIDING ON FATE OF ADVRY IN WRN/NRN CWA AND WILL DECIDE CLOSER TO EXPIRATION (18Z) WHETHER TO CONTINUE OR LET GO. WINDS ARE GETTING A LITTLE PESKY AS MIXING COMMENCES. FINE LINE IS WARMING TEMPS VS. INCREASING WINDS. WC VALUES WL BORDER CRITERIA ALL DAY...AND ONLY ABOUT 5 COUNTIES IN FAR WC MN THAT ARE EXCEEDING CRITERIA NOW. WHILE TEMPS WL SEE LITTLE WARMING...MAY BE JUST ENOUGH TO KEEP ADVRY CHILLS FROM BEING MET. PLENTY OF SUN AND LITTLE SNOW COVER WILL HELP WARMING JUST A BIT...AS SOME INSOLATION WILL OCCUR DESPITE WINDS. SOME JET INDUCED CIRRUS WL CLEAR THE CWA BY 18Z...SO WILL HAVE AN UPDATE THEN TO GO SUNNY...AND CHANGE HEADLINES IF NEEDED. TONIGHT WL BE COLDEST OF YEAR...AND RUC/META H100-H90 WIND CORE TO SHIFT INTO CNTL/ERN CWA BY EVE. LOOKS LIKE ADVRY FOR SURE TONIGHT...QUESTION WL BE HOW FAR WEST TO EXTEND IT. GUIDANCE TEMPS FOR TONIGHT WAY TOO COLD...BUT GIVES INIDICATION OF SEVERITY OF COLD...AS -28C H9 POCKET SLIDES INTO CWA. .MSP...WIND CHILL ADVISORY UNTIL NOON CENTRAL AND WEST CENTRAL MINNESOTA. $$ BINAU mn AREA FORECAST DISCUSSION...UPDATED FOR AVIATION NATIONAL WEATHER SERVICE FORT WORTH TX 450 AM CST WED JAN 22 2003 .AVIATION... ONLY MAJOR CHANGE TO PREVIOUS FCSTS FOR THE N TX TRACON WILL BE TO DELAY THE BREAK OUT CIGS...ALTHOUGH CIGS MOST AREAS (EXCEPT) ACT SHOULD GO VFR BY 20Z AND AFTER...THEN BREAK OUT AFTER 06Z AS SUBSIDENCE TAKES HOLD OVER THE AREA AS SHORTWAVE DEPARTS INTO S TX. PER SOUNDING ANALYSIS AND EXPECTED CAA...I DO FEEL STRONGLY THAT GUIDANCES ARE CLEARING THINGS OUT TOO QUICK FOR THIS EVENING AND WILL HOLD MORE TO ETA/RUC SOUNDINGS WHICH LOOK MORE REALISTIC. OTHERWISE...THE STRONG CAA ENSUING THROUGH TONIGHT SHOULD MAINTAIN THE NLY FLOW AT 10-15 KTS. A FEW GUSTS TO 20 KTS MAY BE POSSIBLE WITH THE CAA HEADING INTO THIS EVENING...BUT WITH LITTLE CERTAINTY ...WILL NOT ADD TO LATER PDS IN THE TAFS. NO PROBS WITH VSBYS. 05/ .EARLY MORNING PUBLIC DISCUSSION 425 AM CST... VERY COLD AIRMASS POISED JUST TO OUR NORTH WILL BE FILTERING INTO NORTH TEXAS OVER THE NEXT 24 HOURS. TEMPERATURES RANGING FROM -25C TO -35C ARE NOTED OVER SOUTHERN ALBERTA...SASKATCHEWAN...AND MANITOBA NOW SPREADING SOUTH INTO NORTHERN MONTANA AND NORTHERN NORTH DAKOTA WHERE TEMPERATURES HAVE FALLEN INTO THE -15C TO -20C RANGE. THIS AIRMASS MEANS BUSINESS AND TEMPERATURES ON THURSDAY WILL STRUGGLE TO REACH FREEZING HERE IN THE METROPLEX...IF WE ARE SO LUCKY. DAY 1 LOW CLOUDS EXPECTED TO LINGER OVER THE AREA ALL DAY TODAY WITH FALLING TEMPERATURES. SHORTWAVE OVER NEW MEXICO APPEARS RATHER POTENT IN WATER VAPOR IMAGERY WITH MID-/HIGH-LEVEL CLOUDS SPREADING EAST INTO CENTRAL TEXAS. RADAR LOOP CONTINUES TO SHOW PRECIPITATION FORMING IN VICINITY OF VORT LOBE OVER CENTRAL/SOUTH-CENTRAL NEW MEXICO MOVING EAST. IT APPEARS THAT RECENT GUIDANCE MAY NOT BE HANDLING THIS FEATURE VERY WELL...ESPECIALLY IN TERMS OF RH FIELD. AM A BIT CONCERNED THAT SOME LIGHT PRECIPITATION MAY AFFECT SOUTHERN ZONES OVERNIGHT TONIGHT AS THIS FEATURE BECOMES SHEARED IN CONFLUENT FLOW OVER THE AREA AND WEAKENS AS IT PASSES. ENOUGH LIFT MAY REMAIN FOR SOME LIGHT PRECIPITATION SOUTH OF THE I-20 CORRIDOR. AS ARCTIC AIR CONTINUES TO SPREAD INTO THE AREA...TEMPERATURES FALLING TO NEAR FREEZING BY LATE TODAY AND BELOW FREEZING OVERNIGHT WOULD SUGGEST THE POTENTIAL FOR LIGHT SLEET OR FREEZING RAIN SHOULD PRECIPITATION FALL. FOR NOW...MAY INCLUDE SLIGHT CHANCE POPS SOUTHERN ZONES FOR TONIGHT BUT ALL SUPPORT FOR PRECIPITATION WILL CEASE BY SUNRISE THURSDAY AS SHORTWAVE SHEARS/WEAKENS AND SUBSIDENCE ENSUES OVER THE AREA. DAY 2 THURSDAY WILL BE QUITE COLD WITH TEMPERATURES STRUGGLING TO REACH FREEZING IN THE METROPLEX...ALTHOUGH SKIES SHOULD BE CLEARING. WITH CLEAR SKIES AND LIGHT WINDS EXPECTED THURSDAY NIGHT TEMPERATURES WILL FALL INTO THE TEENS AREA WIDE. THURSDAY NIGHT/FRIDAY MORNING WILL BRING THE COLDEST TEMPERATURES SO FAR THIS WINTER SEASON TO THE CWA. EXTENDED... NO CHANGES MADE FOR THE EXTENDED PERIOD AT THIS TIME. HOWEVER...LATEST AVN SUGGESTS THAT SUNDAY COULD BE A BIT COOLER THAN ADVERTISED WITH REINFORCING SURGE OF COOLER AIR PROGGED TO MOVE IN EARLY IN THE DAY. I DO NOT FAVOR MAKING DRASTIC CHANGES BASED ON ONE MODEL RUN SO WILL LET FUTURE SHIFTS EXAMINE THIS IN MORE DETAIL. ROBBINS .FWD... TX...NONE. tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 340 PM EST WED JAN 22 2003 12Z RAOBS/LATEST WV LOOP AND RUC ANLSYS SHOW BITTERLY COLD ARCTIC AIRMASS OVR SCNTRL CAN ON NRN FLANK OF FAST NW FLOW ALF DOWNSTREAM OF RDG ALG THE W COAST. 125KT H3 JET MAX OVR NW PLAINS EMBEDDED WITHIN THIS FLOW DRAGGING H5/H7/H85 TEMPS WITHIN CORE OF COLDEST AIR AT CYQD -45/-34/-32C SE INTO UPR LKS...AND SFC TEMPS STILL NR -30F ARND LK WINNIPEG. DESPITE VERY DRY AIR UPSTREAM OF LK SUP (SFC DWPTS AS LO AS -40F) AND SHALLOW NATURE OF COLDEST AIR (INVRN HGT ARND H9 AT INL) COLDER AIR BLOWING ACRS LK SUP HAS CAUSED NMRS LES BANDS TO DVLP OVR AREAS FVRD BY LLVL NW FLOW...AND VSBYS AS LO AS 1/4SM TO 1SM IN SN/BLSN OVR THE W. COMBINATION OF INCRSG WNDS AHD OF ARCTIC SURGE AND TEMPS STILL HOVERING ARND ZERO HAVE CAUSED WND CHILLS AS LO AS -25F OVR THE WRN ZNS EVEN EARLY THIS AFTN...SO HAVE STARTED GOING ADVYS/WRNGS THAT WERE NOT IN EFFECT UNTIL THIS EVNG THIS AFTN OVR THOSE LOCATIONS. MUCH WARMER AIR NOTED AT H85-7 OVR NE CAN AS ATLANTIC AIR ADVECTS SW IN NE FLOW ALF ON BACK SIDE OF CLOSED LO OVR SE CAN. NMRS FCST CONCERNS IN THE SHORT TERM INCLUDING LES/BLSN/WND CHILLS AS WELL AS GOING HEADLINES. AS H3 JET MAX IN NW PLAINS AND ASSOCIATED H5 SHRTWV OVR SCNTRL CAN SLIDE SE TNGT...12Z MODELS SHOW CORE OF COLDEST AIR SLIPPING SE ACRS UPR LKS TNGT. ALL MODELS SHOW PERSISTENCE OF TIGHT PRES GRADIENT/ NWLY LLVL FLOW OVR ENTIRE AREA TNGT...WITH ETA FCST SDNGS SHOWING 25 TO 35KT WNDS WITHIN MIXED LYR ELEVATED BY WRMG FM LK SUP (INVRN HGT UP TO 5K FT DOWNWND OF LK). GFS SHOWS LLVL WND FIELD SHIFTING MORE NNW TNGT WHILE ETA INDICATES NR SFC FLOW WL REMAIN MORE NW. GIVEN DIGGING OF SHRTWV TO THE SW AND TREND OF ETA H925 WNDS TO VEER SIMILAR TO GFS SFC FLOW...SUSPECT GFS WNDS MORE APPROPRIATE. WND DIRECTION IMPORTANT BECAUSE FLOW WL DICTATE LK MODERATION OF TEMP (I.E. WIND CHILL) AS WELL AS LES POTENTIAL. XPCTD LLVL FLOW WL SUPPORT LOWEST MINS OVR GOGEBIC COUNTY PER GFS/ETA H100-85 THKNS FILED WITH GREATEST LK SUP MODERATION E OF MQT. COMPARISON OF FCST H100-85 THKNS AND MINS UPSTREAM WOULD SUG LO TEMP DOWN TO -10F AT IWD (WITH TEMP STEADY AFTR 06Z AS H100-85 THKNS MODIFIES WITH ARRIVAL OF ATLANTIC AIR/MORE NE FLOW WELL ALF LATE TNGT). FCST THKNS OVR THE E WOULD SUPPORT LOWS 0 TO -3F. SUSTAINED WND SPEED OF 20-25 MPH/10 MPH NECESSARY TO ACHIEVE -25F WND CHILL FOR 0 TO -3F/-10F AIR TEMP...SO WND CHILLS E OF MQT-MNM LIKELY TO REACH ADVY CRITERIA ONLY INTERMITTENTLY WHILE ADVY CONDITIONS TO W WL PREDOMINATE. THUS GOING WND CHILL FCST ON TRACK. LES CHART FOR XPCTD CONDITIONS WOULD SUG 4" SN/6 HRS...BUT VERY DRY/COLD AIR AND OBSVD SNFALL DURG THIS COLD OUTBREAK WOULD SUG NO MORE THAN 2"/6 HRS. HOWEVER...WL GO UP TO 3-4"/6 HRS OVR THE ERN ZNS IN LONGER FETCH ACRS WATER AND FCST PASSAGE OF GREATER H85-5 QVECTOR CNVGC/DPVA/H85-5 RH ASSOCIATED WITH DIGGING SHRTWV. SO GOING FCST UP TO 6-8 INCHES OVR THE ERN SN BELTS APPEARS ON TRACK. HAVE OPTED TO GO UP TO 5 INCHES OVR SN BELTS IN ONTONAGON/GOGEBIC COUNTIES TO ACCOUNT FOR SOME ENHANCEMENT FM XPCTD LLVL CNVGC BTWN VEERING LLVL FLOW AND MORE WLY LAND BREEZE THAT MIGHT TRY TO HOLD ON LONGER NR IWD THAN FCST BY GFS (MORE IN LINE WITH ETA FCST). BUT TENDENCY FOR STRENGTH OF LLVL FLOW TO OVERWHELM LAND BREEZE COMPONENT CAN JUSTIFY NO MORE ENHANCEMENT. KEWEENAW/CMX/ BARAGA/MQT ZNS SHUD BE SHIELDED WITH XPCTD FLOW...BUT ERN MQT COUNTY MAY SEE A BIT MORE LES LATER IF FLOW VEERS TO 340. GOING HEADLINES APPEAR APPROPRIATE. EVEN THOUGH SN AMTS MAY NOT JUSTIFY WRNG CRITERIA IN GOGEBIC/ONTONAGON AND ALGER/LUCE/NRN SCHOOLCRAFT... COMBINATION OF SN/BLSN/WND CHILLS JUSTIFY WRNG THESE AREAS. ETA REMAINS MORE AGGRESSIVE THAN GFS IN LWRG INVRN HGT ON THU MRNG AS H5 HGTS RISE IN ADVANCE OF UPR RDGING IN WAKE OF ARCTIC VORTEX SLIPPING S THRU THE GRT LKS. SINCE GFS HAS BETTER HANDLE ON H85 TEMP (I.E. INVRN HGT) THAN ETA OVR NE CAN AND ETA HAS TRENDED SLOWER ON CRASHING INVRN HGT...WL TREND TOWARD SLOWER GFS SOLN. ALTHOUGH LWRG INVRN/INCRSG H85 TEMPS WOULD SUG A DIMINISHING TREND IN LES...INCRSG TEMPS/LESS INHIBITIVE SN GROWTH DYNAMICS MIGHT OFFSET XPCTD TREND TO A CERTAIN EXTENT. SINCE PRES GRADIENT IS FCST TO REMAIN SHARP ACRS THE ENTIRE CWA IN THE MRNG...WL MAINTAIN GOING HEADLINES INTO THU MRNG. HAVE OPTED TO CONT WINTER STORM WRNG INTO THE AFTN OVR THE E BECAUSE DEEPER MSTR/LONGER FETCH FCST TO LINGER THERE UNTIL THE AFTN TO SUPPORT MORE SN...AND GFS/ETA ALSO SHOW HIER WNDS LINGERING LONGER THERE. ADVCTN OF ATLANTIC AIR ALF WL MODERATE LLVL TEMPS ON THU...BUT CHILL IN PLACE NOW JUSTIFIES FOLLOWING LWR GFS/ETA MOS FCST FOR HI TEMPS. CONSIDERING TREND TOWARD DEEPER MSTR REMAINING LONGER AND LINGERING H85-5 QECTOR CNVGC THRU NOON...HAVE UPPED FCST SN AMTS IN THE E TO 6 INCHES. NO MORE THAN 3 INCHES ACRS THE W WITH FASTER ARRIVAL OF DRIER AIR. ARRIVAL OF UPR RDGING/H85-5 QVECTOR DVGC AND MORE ACYC SFC FLOW/DRY AIR SHOULD SUPPRESS LINGERING LES THU NGT...ESPECIALLY OVR THE WCNTRL. HOWEVER...ETA/GFS POINT TOWARD CONTG LLVL CNVGC OVR THE ERN ZNS (ALBEIT WITH LIGHTER WNDS) AS NW LLVL FLOW IN ADVANCE OF SFC RDG MEETS NE LAND BREEZE OFF NRBY ONTARIO. VORTEX MAY SET UP OVR SE LK SUP IN CNVGC BTWN THESE TWO RELATIVELY LGT AIRSTREAMS. BUT LWRG INVRN HGTS (ETA SHOWS INVRN HGT DOWN TO 2K FT WITH LESS DISCREPANCY BTWN GFS/ETA ON H85 TEMP) SUGS THERE WL BE NO MORE THAN A FEW INCHES ADDITIONAL ACCUM. VORTEX MAY ENHANCE LAND BREEZE OVR WCNTRL. COMBINATION OF LGT WLY FLOW AND CLRG SKIES SHUD ALLOW MINS TO FALL TO LWR AVN/ETA MOS GUIDANCE OVR INTERIOR AREAS. MODELS HAVE TRENDED FASTER WITH SHRTWV FCST TO PASS ESE THRU ONTARIO ON FRI. SOME WEAK WAD/ISENTROPIC LIFT FCST TO BEIN DURG THE AFTN... BUT LLVLS ARE SO DRY PER ETA FCST SDNGS TO XPCT MUCH PCPN. ALSO... SHRTWV/ASSOCIATED H85-5 QVECTOR CNVGC TRACKS N OF CWA...WHICH LIES IN UNFVRBL RIGHT EXIT OF SUPPORTING H3 JET MAX. AFTR LINGERING SHSN OVR THE ERN ZNS DIMINISH IN THE MRNG UNDER CONTD MID LVL HGT RISES...WL JUST INDICATE INCRSG HI/MID CLD WITH NO PCPN. APRCH OF ASSOCIATED SFC TROF AND HIER H85-5 QVECTOR CNVGC/RH MAY PROVIDE BETTER FOCUS FOR PCPN THEN. GFS INDICATES LLVL WND FIELD BE TOO W FOR ANY LK ENHANCEMENT OFF LK MI IN ADVANCE OF FNT. COLD FNT PUSHES THRU CWA SAT AFTN...SO PTCHY LGT SN WL EVOLVE INTO PURE LES AS H85 THERMAL TROF WITH TEMPS APRCHG -25C APRCHES DURG AFTN. TEMPS WL MODERATE IN ADVANCE OF BNDRY ON FRI...THEN NOT FALL TOO FAR FRI NGT WITH FAIRLY TIGHT PRES GRADIENT IN PLACE. MOS FCST TEMPS IN DECENT AGREEMENT AND SEEM APPROPRIATE. 00Z/06Z OPERATIONAL EXTENDED MODELS/ENSEMBLES POINT TOWARD A MORE VIGOROUS ARCTIC INTRUSION SAT NGT FOLLOWING THE SHRTWV RESPONSIBLE FOR SN CHCS FRI NGT/SAT. WL GO LIKELY SHSN FOR THE SN BELTS FVRD WITH NW FLOW SAT NGT INTO SUN (CHC SHSN/FLURRIES ELSEWHERE) AND LWR GOING FCST TEMPS TO REFLECT TREND TOWARD H85 TEMPS DROPPING TOWARD -25C AGAIN (VS -20C FCST YDAY). 12Z MODELS CONFIRM THIS TREND. LES SHUD DIMINISH LATER ON SUN AS ARCTIC HI PRES BLDS OVHD. VERY GOOD AGREEMENT INDICATING VIGOROUS WAD PATTERN SETTING UP ON MON AS ARCTIC HI PRES CENTER SHIFTS TO E AND INCRSGLY ZONAL FLOW ALF CAUSES STEEP PRES FALLS ACRS SW CAN/NRN PLAINS. GOING FCST CHC SN WITH EASING CHILL ON MON STILL ON TARGET. THEN ZONAL FLOW WITH ABV NORMAL H5 HGTS TO PREDOMINATE STARTING TUE. XCPT ONLY SHALLOW COLD AIR (NO LES) TO FILL IN BEHIND LO PRES/CHC SN ON TUE...WITH SOME SUNSHINE ALLOWING WELL ABV NORMAL TEMPS ON WED. COORDINATED WITH DLH/APX/GRB. .MQT...WINTER STORM WARNING INTO THU MORNING MIZ002-009. WINTER STORM WARNING INTO THU AFTN 006-007-085. WINTER WEATHER ADVY INTO THU MORNING MIZ001-003. WIND CHILL ADVY INTO THU MORNING MIZ004-005-010-011-012-084. HEAVY FREEZING SPRAY WARNING LAKE SUPERIOR. KC mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ST LOUIS MO 305 PM CST WED JAN 22 2003 MAIN CONCERN CONTINUES TO DEAL WITH WIND CHILLS TONIGHT AND TOMORROW MORNING AND PLAN ON KEEPING ADVISORY AS IS. WILL TRIM GUIDANCE LOWS TONIGHT BY A CATEGORY FROM COU TO FAM TO ACCOUNT FOR THE MINOR ACCUMULATIONS AND GO WITH A CONSESUS OF GUIDANCE ELSEWHERE. WITH WINDS STAYING IN THE 10 TO 20 MPH...CURRENT PROJECTED WIND CHILLS STILL LOOK ON TRACK. GFS/ETA SHOW REASONABLE AGREEMENT WITH MASS FIELDS NEXT FEW DAYS GIVING MODEST CONFIDENCE TO FORECAST. RADAR MOSAIC CURRENTLY SHOWING AXIS OF SNOW BAND EXTENDING FROM SOUTH OF KANSAS CITY THROUGH SRN HALF OF MY CWA. THIS LINES UP WELL WITH ETA/RUC DEPICTION OF MID LEVEL FRONTOGENTICAL FORCING THAT MOVES QUICKLY SOUTHEAST OF THE REGION THIS EVENING. WILL MENTION EARLY EVENING SNOW MAINLY IN THE SRN SECTIONS THIS EVENING WITH MINOR ADDITIONAL ACCUMULATIONS. BEYOND THIS EVENING...FORECAST LOOKS DRY GOING INTO THURSDAY. SFC HIGH CENTERED OVER THE CANADIAN PRAIRIES WILL MOVE SOUTHEASTWARD ACROSS MO/IL THU NIGHT. WARM AIR ADVECTION KICKS IN ON FRIDAY AS HIGH PASSES TO THE EAST. CURRENTLY HAVE A CHANCE FOR LIGHT SNOW IN THE ZONES GIVEN THE WAA...BUT WILL TAKE IT OUT OF THE SRN AND WRN COUNTIES. OTHERWISE...WILL STAY ON THE COOL SIDE OF GUIDANCE FOR TEMPS TOMORROW AND TOMORROW NIGHT. HAVE SOME CONFIDENCE IN THE EXTENDED AS MODELS ARE SHOWING GENERAL AGREEMENT WITH THE UPPER PATTERN BECOMING MORE ZONAL NEXT WEEK. WITH THAT SAID...MEDIUM RANGE MODELS HAVE DISAGREEMENTS WITH INDIVIDUAL SHORTWAVE TROFS WITH THE ECMWF MOVING ONE THROUGH LATE TUESDAY WITH THE GFS A DAY LATER. LOOKS LIKE ENOUGH FORCING AND ASSOCIATED MOISTURE WILL BE PRESENT ACCORDING TO 12Z GFS TO ADD CHC OF SNOW SAT NIGHT...AND LEAVE REST OF EXTENDED DRY. ENSEMBLE MOS MEAN TEMPS ARE CLOSE TO OPERATIONAL GFS NUMBERS...SO WILL FOLLOW. .STL...WIND CHILL ADVISORY THROUGH THURSDAY MORNING FOR THE ENTIRE CWA. BRITT mo AREA FORECAST DISCUSSION...UPDATED FOR AVIATION DISCUSSION NATIONAL WEATHER SERVICE FORT WORTH TX 1123 AM CST WED JAN 22 2003 ...AVIATION DISCUSSION: A FEW BREAKS IN LOW CLOUDS NOTED IN VISIBLE IMAGERY...ALTHOUGH BEST AREA OF CLEARING TO EAST OF METROPLEX SHOWS A TENDENCY TO DEVELOP SW AND NOT TOWARDS METRO AIRPORTS. NEVERTHELESS...BELIEVE SOME BREAKS WILL DEVELOP THROUGH 00Z THOUGH NOT ENOUGH TO SUGGEST GOING SCATTERED WITH LOW CLOUDS. CEILINGS HAVE GENERALLY NOT IMPROVED THIS MORNING AND BASED ON RUC FORECAST SOUNDINGS ONLY SLOWLY INCREASING CEILING HEIGHTS ARE ANTICIPATED THROUGH THIS AFTERNOON. AS COLD AIR DEEPENS MORE THIS EVENING CLOUD HEIGHTS WILL INCREASE TO 040-050. SURFACE WINDS WILL CONTINUE FROM AROUND 360 AT 10-15KT AND WITH A SHOT OF COLD AIR ADVECTON/PRESSURE RISES THIS EVENING WILL KEEP CURRENT FORECAST OF AROUND 15KT WITH SOME GUSTINESS FOR LATE THIS AFTERNOON/EVENING. ...07/BB... UPDATED DISCUSSION FROM 1039 AM: WHILE THERE REMAINS EXTENSIVE CLOUD COVER THIS MORNING...MAIN CONCERN IS HOW MUCH EROSION WILL OCCUR DURING THE NEXT FEW HOURS. AT THE CURRENT TIME THERE ARE TWO DISTINCT BREAKS...ONE IN THE EAST AND ONE IN THE WEST...BOTH ERODING TOWARD THE CENTRAL PORTIONS OF THE CWA...BUT NEITHER WITH MUCH MOVEMENT NORTH OR SOUTH. WE EXPECT THIS EROSION TO CONTINUE...ALTHOUGH SOME AREAS WILL REMAIN CLOUDY...WITH PERHAPS A LARGER PORTION SEEING BREAKS. HENCE...WILL GO WITH MOSTLY CLOUDY THIS AFTERNOON...AND KEEP TEMPS FAIRLY STEADY. WILL LEAVE THE REMAINDER OF THE FORECAST ALONE FOR NOW. 42 .FWD... TX...NONE. tx